Quality of service policy sets

ABSTRACT

Disclosed are systems, computer-readable mediums, and methods for receiving client quality of service values associated with a first client. Client metrics of a volume in a storage system are determined for the first client. The client metrics reflect usage of the storage system by the first client. A client load value based is determined upon the client metrics. A quality of service management policy for the first client is determined from a plurality of quality of service management policies based upon the client load value. Each quality of service management policy comprises a formula based on a quality of service parameter. A client target performance value is determined based upon the formula of the quality of service management policy and the received client quality of service values. Performance of the storage system is adjusted for the first client based upon the client target performance value.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/856,997, filed on Apr. 4, 2014, which is a continuation ofInternational Application No. PCT/US12/71844, filed Dec. 27, 2012, whichis a continuation-in-part of U.S. application Ser. No. 13/338,039, filedDec. 27, 2011, and also claims the benefit of U.S. ProvisionalApplication No. 61/697,905, filed Sep. 7, 2012, the entirety of each areincorporated herein by reference.

BACKGROUND

The following description is provided to assist the understanding of thereader. None of the information provided is admitted to be prior art.

In data storage architectures, a client's data may be stored in avolume. Typically, the volume's data resides on a small percentage ofdrives in a storage cluster. This arrangement leads to issues of hotspots where portions of the cluster are over-utilized while otherportions of the cluster are under-utilized. For example, if a client isperforming a large number of accesses of data in the volume, the loadattributed to the small percentage of drives in which the data is storedincreases, resulting in a hot spot. This arrangement may result in aclient experience that is inconsistent across all volumes of the clusteras some clients may experience good performance if their data is storedon portions that are under-utilized and some clients experience poorperformance if their data is stored on over-utilized portions.

One way of attempting to provide a better client experience is usingquality of service based on client prioritization. For example, clientsmay be assigned different priority levels. Based on these prioritylevels, access requests (e.g., read and write requests) for variousclients are prioritized. Clients' access requests are dispatched basedon the load of the cluster and a priority assigned to each client. Forexample, a client having a higher priority may have more access requestsprocessed than another client having a lower priority during times whenthe cluster is experiencing higher load. Using the priority system onlyallows for a slightly better client experience. For example, prioritiesdo not guarantee a specific, consistent level of performance and arebased on the idea that the cluster is dividing its full performanceamong all clients all the time. One reason for this is that a singleclient's effects on performance of the cluster are not capped, when thesystem is stressed, the system always runs slow regardless of how manycustomers are on the system since it is still running prioritized.Prioritization also makes it difficult for customer to understand theactual performance they are receiving, because prioritization does notextend an understandable idea to customers of the actual performance thecustomers are getting. Also, prioritization does not allowadministrators to control how the system supports multiple customers andhow the customers drive the system to load.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings.

FIG. 1A depicts a simplified system for performance management in astorage system in accordance with an illustrative implementation.

FIG. 1B depicts a more detailed example of a system in accordance withan illustrative implementation.

FIG. 2 depicts a user interface for setting quality of serviceparameters in accordance with an illustrative implementation.

FIG. 3 depicts a simplified flowchart of a method of performingperformance management in accordance with an illustrativeimplementation.

FIG. 4 depicts a more detailed example of adjusting performance using aperformance manager in accordance with an illustrative implementation.

FIG. 5 depicts a performance curve comparing the size of input/outputoperations with system load in accordance with an illustrativeimplementation.

FIG. 6 depicts a simplified flowchart of a method of performingperformance management that matches an overloaded system metric with aclient metric in accordance with an illustrative implementation.

FIG. 7 depicts a graph of a number of IOPS performed by client over atime period in accordance with an illustrative implementation.

FIG. 8 shows an example QoS Interface GUI 800 which may be configured ordesigned to enable service providers, users, and/or other entities todynamically define and/or create different performance classes of useand/or to define performance/QoS related customizations in the storagesystem in accordance with an illustrative implementation.

FIG. 9 shows a portion of a storage system in accordance with anillustrative implementation.

FIG. 10 illustrates a specific example embodiment of a LOAD-Service datastructure.

FIG. 11 illustrates an alternate example embodiment of a LOAD-Servicedata structure 1100 which may be configured or designed for trackingsystem load characteristics and conditions associated with differentservices which are running within the storage system.

FIG. 12 illustrates a specific example embodiment of a Client-Servicedata structure.

FIG. 13A shows a flow diagram of a LOAD(Service) Analysis Procedure inaccordance with an illustrative implementation.

FIG. 13B shows a flow diagram of a LOAD(Read) Analysis Procedure inaccordance with an illustrative implementation.

FIG. 13C shows a flow diagram of a LOAD(Write) Analysis Procedure inaccordance with an illustrative implementation.

FIG. 14 shows a flow diagram of a LOAD(Client) Analysis Procedure inaccordance with an illustrative implementation.

FIG. 15 shows a flow diagram of a QoS Client Policy Management Procedurein accordance with an illustrative implementation.

FIG. 16 shows a flow diagram of a QoS Client-Read Policy ManagementProcedure in accordance with an illustrative implementation.

FIG. 17 shows a flow diagram of a QoS Client-Write Policy ManagementProcedure in accordance with an illustrative implementation.

FIG. 18 shows a graphical representation illustrating how the storagesystem implements aspects of a QoS Client Policy Management Proceduresuch as that illustrated in FIG. 15 in accordance with an illustrativeimplementation.

FIG. 19A shows a graphical representation illustrating how different QoSManagement Policy Sets for throttling Client IOPS can be automaticallyand/or dynamically implemented in response changing Load(Client)conditions in accordance with an illustrative implementation.

FIG. 19B shows a graphic representation illustrating how QoS Managementand IOPS throttling may be simultaneously, independently, anddynamically implemented for multiple different clients of the storagesystem in accordance with an illustrative implementation.

FIG. 20 shows a graphical representation illustrating how different QoSManagement Policy Sets for throttling Client IOPS can be automaticallyand/or dynamically implemented in response changing Load(Client-Read)conditions in accordance with an illustrative implementation.

FIG. 21 shows a graphical representation illustrating how different QoSManagement Policy Sets for throttling Client IOPS can be automaticallyand/or dynamically implemented in response changing Load(Client-Write)conditions in accordance with an illustrative implementation.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

In general, one aspect of the subject matter described in thisspecification can be embodied in methods for determining client metricsof a volume in a storage system for a first client of a plurality ofclients. The storage system stores data from the plurality of clients.System metrics of a cluster in the storage system are determined basedupon use of the storage system by the plurality of clients. A load valueof the storage system is determined based upon the system metrics andthe client metrics. The load value is determined to be above apredefined threshold. A target performance value is calculated basedupon the load value, a minimum quality of service value, and a maximumquality of service value. Performance of the storage system is adjustedfor the client based upon the target performance value and thedetermining the load value is above the predefined threshold. Otherimplementations of this aspect include corresponding systems,apparatuses, and computer-readable media configured to perform theactions of the method.

Another aspect of the subject matter described in this specification canbe embodied in methods for managing performance in a storage systemstoring data for a plurality of data volumes, wherein an individual datavolume has an associated client. A selection of a performance class ofuse for an individual data volume is received. The performance class ofuse is selected from a plurality of performance classes in which atleast one performance class of use has a different Input Output PerSecond (IOPS) quality of service parameter. Access to the individualdata volume is managed based on the IOPS quality of service parameter ofthe selected performance class of use. Other implementations of thisaspect include corresponding systems, apparatuses, and computer-readablemedia configured to perform the actions of the method.

Another aspect of the subject matter described in this specification canbe embodied in methods for determining a load value associated withaccess of data stored in a storage system for a client. The data isdivided into a plurality of blocks and are stored substantially evenlyacross a plurality of nodes of the storage system. The storage systemincludes data from a plurality of clients. A requested quality ofservice parameter from the client is received. Access of the dataaccording to the requested quality of service parameter is monitored.Access to the data is throttled based upon the monitoring access of thedata. Other implementations of this aspect include correspondingsystems, apparatuses, and computer-readable media configured to performthe actions of the method.

Another aspect of the subject matter described in this specification canbe embodied in methods for determining an input/output operations persecond (IOPS) metric associated with access of data stored in a storagesystem for a client. The data is divided into a plurality of blocks andthe plurality of blocks are stored substantially evenly across aplurality of nodes of the storage system. The storage system includesdata from a plurality of clients. A requested IOPS value is received.Access to the data is relegated based upon the requested IOPS value.Other implementations of this aspect include corresponding systems,apparatuses, and computer-readable media configured to perform theactions of the method.

Another aspect of the subject matter described in this specification canbe embodied in methods for receiving a minimum performance quality ofservice parameter associated with a compute device accessing a storagesystem volume. System metrics associated with the storage system volumeare received. A target performance value associated with the computedevice is calculated based on the minimum performance quality of servicemetrics and the system metrics. The target performance value is sent toa controller module when the target performance value satisfies theminimum performance quality of service metric such that the controllermodule limits a performance of the compute device accessing the storagesystem volume to the target performance value. Other implementations ofthis aspect include corresponding systems, apparatuses, andcomputer-readable media configured to perform the actions of the method.

Another aspect of the subject matter described in this specification canbe embodied in methods for determining a total amount of capacity for astorage system. The capacity is defined by a quality of serviceparameter. A plurality of values of the quality of service parameterthat are provisioned for a plurality of clients to access the storagesystem are received. Each client in the plurality of clients isprovisioned with a value of the quality of service parameter. Theplurality of values that are provisioned for the plurality of clients inthe storage system are monitored and determined if the plurality ofvalues violate a threshold. The threshold being based on the totalamount of capacity for the storage system. A signal is automaticallyoutput when the plurality of values violate the threshold to indicate anadjustment in a value of the quality of service parameter for one ormore clients or the total amount of capacity for the storage systemshould be performed. Other implementations of this aspect includecorresponding systems, apparatuses, and computer-readable mediaconfigured to perform the actions of the method.

Another aspect of the subject matter described in this specification canbe embodied in methods for provisioning a plurality of clients withquality of service parameters to access a storage system. Access of thestorage system by the plurality of clients is monitored. Performance ofa client in the plurality of clients in accessing the storage system ismonitored. The performance of the client in accessing the storage systemis controlled based on the quality of service parameters in which theclient is provisioned. The performance of the client and the access ofthe storage system by the plurality of clients is analyzed to determinea target performance value for the client. Control of the client inaccessing the storage system is dynamically adjusted to adjust theperformance of the client based on the quality of service parameters.Other implementations of this aspect include corresponding systems,apparatuses, and computer-readable media configured to perform theactions of the method.

Another aspect of the subject matter described in this specification canbe embodied in methods for provisioning a plurality of clients with aquality of service parameters to access a storage system. Performance ofa client in the plurality of clients in accessing the storage system ismonitored. The performance of the client in accessing the storage systemis independently controlled based on the quality of service parametersin which the client is provisioned without regard to quality of serviceparameters provisioned for other clients in the plurality of clients. Aload value for the client is calculated based upon the use of thestorage system by the client and the quality of service parameters. Theperformance of the client is analyzed with respect to the quality ofservice parameters for the client to determine a difference between theperformance and the load value. Access to resources of the storagesystem is dynamically allocated to independently adjust control of theperformance of the client based on the difference between theperformance and the load value. Other implementations of this aspectinclude corresponding systems, apparatuses, and computer-readable mediaconfigured to perform the actions of the method.

Another aspect of the subject matter described in this specification canbe embodied in methods for adjusting client access to data within aserver system. A volume server in communication with the client receivesa request from the client to access data. A performance manager monitorsmetrics and adjusts the client's access to the data in response tocomparing the metrics against a target value. Other implementations ofthis aspect include corresponding systems, apparatuses, andcomputer-readable media configured to perform the actions of the method.

Another aspect of the subject matter described in this specification canbe embodied in methods for adjusting access by a client to data within aserver system. A target value indicating a target client metric isreceived. A request by the client to access the data within the serversystem is received. The client performance is compared to the targetvalue and based upon the comparison to the target value, the client'saccess to the data is adjusted.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects,implementations, and features described above, further aspects,implementations, and features will become apparent by reference to thefollowing drawings and the detailed description.

Specific Example Embodiments

One or more different inventions may be described in the presentapplication. Further, for one or more of the invention(s) describedherein, numerous embodiments may be described in this patentapplication, and are presented for illustrative purposes only. Thedescribed embodiments are not intended to be limiting in any sense. Oneor more of the invention(s) may be widely applicable to numerousembodiments, as is readily apparent from the disclosure. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice one or more of the invention(s), and it is to beunderstood that other embodiments may be utilized and that structural,logical, software, electrical and other changes may be made withoutdeparting from the scope of the one or more of the invention(s).Accordingly, those skilled in the art will recognize that the one ormore of the invention(s) may be practiced with various modifications andalterations. Particular features of one or more of the invention(s) maybe described with reference to one or more particular embodiments orfigures that form a part of the present disclosure, and in which areshown, by way of illustration, specific embodiments of one or more ofthe invention(s). It should be understood, however, that such featuresare not limited to usage in the one or more particular embodiments orfigures with reference to which they are described. The presentdisclosure is neither a literal description of all embodiments of one ormore of the invention(s) nor a listing of features of one or more of theinvention(s) that must be present in all embodiments.

Headings of sections provided in this patent application and the titleof this patent application are for convenience only, and are not to betaken as limiting the disclosure in any way. Devices that are incommunication with each other need not be in continuous communicationwith each other, unless expressly specified otherwise. In addition,devices that are in communication with each other may communicatedirectly or indirectly through one or more intermediaries. A descriptionof an embodiment with several components in communication with eachother does not imply that all such components are required. To thecontrary, a variety of optional components are described to illustratethe wide variety of possible embodiments of one or more of theinvention(s).

Further, although process steps, method steps, algorithms or the likemay be described in a sequential order, such processes, methods andalgorithms may be configured to work in alternate orders. In otherwords, any sequence or order of steps that may be described in thispatent application does not, in and of itself, indicate a requirementthat the steps be performed in that order. The steps of describedprocesses may be performed in any order practical. Further, some stepsmay be performed simultaneously despite being described or implied asoccurring non-simultaneously (e.g., because one step is described afterthe other step). Moreover, the illustration of a process by itsdepiction in a drawing does not imply that the illustrated process isexclusive of other variations and modifications thereto, does not implythat the illustrated process or any of its steps are necessary to one ormore of the invention(s), and does not imply that the illustratedprocess is preferred.

When a single device or article is described, it will be readilyapparent that more than one device/article (whether or not theycooperate) may be used in place of a single device/article. Similarly,where more than one device or article is described (whether or not theycooperate), it will be readily apparent that a single device/article maybe used in place of the more than one device or article. Thefunctionality and/or the features of a device may be alternativelyembodied by one or more other devices that are not explicitly describedas having such functionality/features. Thus, other embodiments of one ormore of the invention(s) need not include the device itself.

Techniques and mechanisms described or reference herein will sometimesbe described in singular form for clarity. However, it should be notedthat particular embodiments include multiple iterations of a techniqueor multiple instantiations of a mechanism unless noted otherwise.

DETAILED DESCRIPTION

Described herein are techniques for a performance management storagesystem. In the following description, for purposes of explanation,numerous examples and specific details are set forth in order to providea thorough understanding of various implementations. Particularimplementations as defined by the claims may include some or all of thefeatures in these examples alone or in combination with other featuresdescribed below, and may further include modifications and equivalentsof the features and concepts described herein.

Storage System

FIG. 1A depicts a simplified system for performance management in astorage system 100 in accordance with an illustrative implementation.System 100 includes a client layer 102, a metadata layer 104, a blockserver layer 106, and storage 116.

Before discussing how particular implementations manage performance ofclients 108, the structure of a possible system is described. Clientlayer 102 includes one or more clients 108 a-108 n. Clients 108 includeclient processes that may exist on one or more physical machines. Whenthe term “client” is used in the disclosure, the action being performedmay be performed by a client process. A client process is responsiblefor storing, retrieving, and deleting data in system 100. A clientprocess may address pieces of data depending on the nature of thestorage system and the format of the data stored. For example, theclient process may reference data using a client address. The clientaddress may take different forms. For example, in a storage system thatuses file storage, client 108 may reference a particular volume orpartition, and a file name. With object storage, the client address maybe a unique object name. For block storage, the client address may be avolume or partition, and a block address. Clients 108 communicate withmetadata layer 104 using different protocols, such as small computersystem interface (SCSI), Internet small computer system interface(ISCSI), fibre channel (FC), common Internet file system (CIFS), networkfile system (NFS), hypertext transfer protocol (HTTP), web-baseddistributed authoring and versioning (WebDAV), or a custom protocol.

Metadata layer 104 includes one or more metadata servers 110 a-110 n.Performance managers 114 may be located on metadata servers 110 a-110 n.Block server layer 106 includes one or more block servers 112 a-112 n.Block servers 112 a-112 n are coupled to storage 116, which storesvolume data for clients 108. Each client 108 may be associated with avolume. In one implementation, only one client 108 accesses data in avolume; however, multiple clients 108 may access data in a singlevolume.

Storage 116 can include multiple solid state drives (SSDs). In oneimplementation, storage 116 can be a cluster of individual drivescoupled together via a network. When the term “cluster” is used, it willbe recognized that cluster may represent a storage system that includesmultiple disks that may not be networked together. In oneimplementation, storage 116 uses solid state memory to store persistentdata. SSDs use microchips that store data in non-volatile memory chipsand contain no moving parts. One consequence of this is that SSDs allowrandom access to data in different drives in an optimized manner ascompared to drives with spinning disks. Read or write requests tonon-sequential portions of SSDs can be performed in a comparable amountof time as compared to sequential read or write requests. In contrast,if spinning disks were used, random read/writes would not be efficientsince inserting a read/write head at various random locations to readdata results in slower data access than if the data is read fromsequential locations. Accordingly, using electromechanical disk storagecan require that a client's volume of data be concentrated in a smallrelatively sequential portion of the cluster to avoid slower data accessto non-sequential data. Using SSDs removes this limitation.

In various implementations, non-sequentially storing data in storage 116is based upon breaking data up into one more storage units, e.g., datablocks. A data block, therefore, is the raw data for a volume and may bethe smallest addressable unit of data. The metadata layer 104 or theclient layer 102 can break data into data blocks. The data blocks canthen be stored on multiple block servers 112. Data blocks can be of afixed size, can be initially a fixed size but compressed, or can be of avariable size. Data blocks can also be segmented based on the contextualcontent of the block. For example, data of a particular type may have alarger data block size compared to other types of data. Maintainingsegmentation of the blocks on a write (and corresponding re-assembly ona read) may occur in client layer 102 and/or metadata layer 104. Also,compression may occur in client layer 102, metadata layer 104, and/orblock server layer 106.

In addition to storing data non-sequentially, data blocks can be storedto achieve substantially even distribution across the storage system. Invarious examples, even distribution can be based upon a unique blockidentifier. A block identifier can be an identifier that is determinedbased on the content of the data block, such as by a hash of thecontent. The block identifier is unique to that block of data. Forexample, blocks with the same content have the same block identifier,but blocks with different content have different block identifiers. Toachieve even distribution, the values of possible unique identifiers canhave a uniform distribution. Accordingly, storing data blocks based uponthe unique identifier, or a portion of the unique identifier, results inthe data being stored substantially evenly across drives in the cluster.

Because client data, e.g., a volume associated with the client, isspread evenly across all of the drives in the cluster, every drive inthe cluster is involved in the read and write paths of each volume. Thisconfiguration balances the data and load across all of the drives. Thisarrangement also removes hot spots within the cluster, which can occurwhen client's data is stored sequentially on any volume.

In addition, having data spread evenly across drives in the clusterallows a consistent total aggregate performance of a cluster to bedefined and achieved. This aggregation can be achieved, since data foreach client is spread evenly through the drives. Accordingly, a client'sI/O will involve all the drives in the cluster. Since, all clients havetheir data spread substantially evenly through all the drives in thestorage system, a performance of the system can be described inaggregate as a single number, e.g., the sum of performance of all thedrives in the storage system.

Block servers 112 and slice servers 124 maintain a mapping between ablock identifier and the location of the data block in a storage mediumof block server 112. A volume includes these unique and uniformly randomidentifiers, and so a volume's data is also evenly distributedthroughout the cluster.

Metadata layer 104 stores metadata that maps between client layer 102and block server layer 106. For example, metadata servers 110 mapbetween the client addressing used by clients 108 (e.g., file names,object names, block numbers, etc.) and block layer addressing (e.g.,block identifiers) used in block server layer 106. Clients 108 mayperform access based on client addresses. However, as described above,block servers 112 store data based upon identifiers and do not storedata based on client addresses. Accordingly, a client can access datausing a client address which is eventually translated into thecorresponding unique identifiers that reference the client's data instorage 116.

Although the parts of system 100 are shown as being logically separate,entities may be combined in different fashions. For example, thefunctions of any of the layers may be combined into a single process orsingle machine (e.g., a computing device) and multiple functions or allfunctions may exist on one machine or across multiple machines. Also,when operating across multiple machines, the machines may communicateusing a network interface, such as a local area network (LAN) or a widearea network (WAN). In one implementation, one or more metadata servers110 may be combined with one or more block servers 112 in a singlemachine. Entities in system 100 may be virtualized entities. Forexample, multiple virtual block servers 112 may be included on amachine. Entities may also be included in a cluster, where computingresources of the cluster are virtualized such that the computingresources appear as a single entity.

FIG. 1B depicts a more detailed example of system 100 according to oneimplementation. Metadata layer 104 may include a redirector server 120and multiple volume servers 122. Each volume server 122 may beassociated with a plurality of slice servers 124.

In this example, client 108 a wants to connect to a volume (e.g., clientaddress). Client 108 a communicates with redirector server 120,identifies itself by an initiator name, and also indicates a volume bytarget name that client 108 a wants to connect to. Different volumeservers 122 may be responsible for different volumes. In this case,redirector server 120 is used to redirect the client to a specificvolume server 122. To client 108, redirector server 120 may represent asingle point of contact. The first request from client 108 a then isredirected to a specific volume server 122. For example, redirectorserver 120 may use a database of volumes to determine which volumeserver 122 is a primary volume server for the requested target name. Therequest from client 108 a is then directed to the specific volume server122 causing client 108 a to connect directly to the specific volumeserver 122. Communications between client 108 a and the specific volumeserver 122 may then proceed without redirector server 120.

Volume server 122 performs functions as described with respect tometadata server 110. Additionally, each volume server 122 includes aperformance manager 114. For each volume hosted by volume server 122, alist of block identifiers is stored with one block identifier for eachlogical block on the volume. Each volume may be replicated between oneor more volume servers 122 and the metadata for each volume may besynchronized between each of the volume servers 122 hosting that volume.If volume server 122 fails, redirector server 120 may direct client 108to an alternate volume server 122.

In one implementation, the metadata being stored on volume server 122may be too large for one volume server 122. Thus, multiple slice servers124 may be associated with each volume server 122. The metadata may bedivided into slices and a slice of metadata may be stored on each sliceserver 124. When a request for a volume is received at volume server122, volume server 122 determines which slice server 124 containsmetadata for that volume. Volume server 122 then routes the request tothe appropriate slice server 124. Accordingly, slice server 124 adds anadditional layer of abstraction to volume server 122.

The above structure allows storing of data evenly across the cluster ofdisks. For example, by storing data based on block identifiers, data canbe evenly stored across drives of a cluster. As described above, dataevenly stored across the cluster allows for performance metrics tomanage load in system 100. If the system 100 is under a load, clientscan be throttled or locked out of a volume. When a client is locked outof a volume, metadata server 110 or volume server 122 may close thecommand window or reduce or zero the amount of read or write data thatis being processed at a time for client 108. The metadata server 110 orthe volume server 122 can queue access requests for client 108, suchthat IO requests from the client 108 can be processed after the client'saccess to the volume resumes after the lock out period.

Performance Metrics and Load of the Storage System

The storage system 100 can also include a performance manager 114 thatcan monitor clients' use of the storage system's resources. In addition,performance manager 114 can regulate the client's use of the storagesystem 100. The client's use of the storage system can be adjusted basedupon performance metrics, the client's quality of service parameters,and the load of the storage system. Performance metrics are variousmeasurable attributes of the storage system. One or more performancemetrics can be used to calculate a load of the system, which, asdescribed in greater detail below, can be used to throttle clients ofthe system.

Performance metrics can be grouped in different categories of metrics.System metrics is one such category. System metrics are metrics thatreflect the use of the system or components of the system by allclients. System metrics can include metrics associated with the entirestorage system or with components within the storage system. Forexample, system metrics can be calculated at the system level, clusterlevel, node level, service level, or drive level. Space utilization isone example of a system metric. The cluster space utilization reflectshow much space is available for a particular cluster, while the drivespace utilization metric reflects how much space is available for aparticular drive. Space utilization metrics can also be determined forat the system level, service level, and the node level. Other examplesof system metrics include measured or aggregated metrics such as readlatency, write latency, input/output operations per second (IOPS), readIOPS, write IOPS, I/O size, write cache capacity, dedupe-ability,compressibility, total bandwidth, read bandwidth, write bandwidth,read/write ratio, workload type, data content, data type, etc.

IOPS can be real input/output operations per second that are measuredfor a cluster or drive. Bandwidth may be the amount of data that isbeing transferred between clients 108 and the volume of data. Readlatency can be the time taken for the system 100 to read data from avolume and return the data to a client. Write latency can be the timetaken for the system to write data and return a success indicator to theclient. Workload type can indicate if IO access is sequential or random.The data type can identify the type of data being accessed/written,e.g., text, video, images, audio, etc. The write cache capacity refersto a write cache or a node, a block server, or a volume server. Thewrite cache is relatively fast memory that is used to store data beforeit is written to storage 116. As noted above, each of these metrics canbe independently calculated for the system, a cluster, a node, etc. Inaddition, these values can also be calculated at a client level.

Client metrics are another category of metrics that can be calculated.Unlike system metrics, client metrics are calculated taking into accountthe client's use of the system. As described in greater detail below, aclient metric may include use by other client's that are using commonfeatures of the system. Client metrics, however, will not include use ofnon-common features of the system by other clients. In oneimplementation, client metrics can include the same metrics as thesystem metrics, but rather than being component or system wide, arespecific to a volume of the client. For example, metrics such as readlatency or write IOPS can be monitored for a particular volume of aclient.

Metrics, both system and client, can be calculated over a period oftime, e.g., 250 ms, 500 ms, 1 s, etc. Accordingly, different values suchas a min, max, standard deviation, average, etc., can be calculated foreach metric. One or more of the metrics can be used to calculate a valuethat represents a load of the storage system. As described in greaterdetail below, various different load calculations can be calculated.Loads can be calculated for the storage system as a whole, forindividual components, for individual services, and/or individualclients. Load values, e.g., system load values and/or client loadvalues, can then be used by the quality of service system to determineif and how clients should be throttled.

As described in greater detail below, performance for individual clientscan be adjusted based upon the monitored metrics. For example, based ona number of factors, such as system metrics, client metrics, and clientquality of service parameters, a number of IOPS that can be performed bya client 108 over a period of time may be managed. In oneimplementation, performance manager 114 regulates the number of IOPSthat are performed by locking client 108 out of a volume for differentamounts of time to manage how many IOPS can be performed by client 108.For example, when client 108 is heavily restricted, client 108 may belocked out of accessing a volume for 450 milliseconds every 500milliseconds and when client 108 is not heavily restricted, client 108is blocked out of a volume every 50 milliseconds for every 500milliseconds. The lockout effectively manages the number of IOPS thatclient 108 can perform every 500 milliseconds. Although examples usingIOPS are described, other metrics may also be used, as will be describedin more detail below.

The use of metrics to manage load in system 100 is possible because aclient's effect on global cluster performance is predictable due to theevenness of distribution of data, and therefore, data load. For example,by locking out client 108 from accessing the cluster, the load in thecluster may be effectively managed. Because load is evenly distributed,reducing access to the client's volume reduces that client's load evenlyacross the cluster. However, conventional storage architectures wherehot spots may occur result in unpredictable cluster performance. Thus,reducing access by a client may not alleviate the hot spots because theclient may not be accessing the problem areas of the cluster. Because inthe described embodiment, client loads are evenly distributed throughthe system, a global performance pool can be calculated and individualclient contributions to how the system is being used can also becalculated.

Client Quality of Service Parameters

In addition to system metrics and client metrics, client quality ofservice (QoS) parameters can be used to affect how a client uses thestorage system. Unlike metrics, client QoS parameters are not measuredvalues, but rather variables than can be set that define the desired QoSbounds for a client. Client QoS parameters can be set by anadministrator or a client. In one implementation, client QoS parametersinclude minimum, maximum, and max burst values. Using IOPS as anexample, a minimum IOPS value is a proportional amount of performance ofa cluster for a client. Thus, the minimum IOPS is not a guarantee thatthe volume will always perform at this minimum IOPS value. When a volumeis in an overload situation, the minimum IOPS value is the minimumnumber of IOPS that the system attempts to provide the client. However,based upon cluster performance, an individual client's IOPS may be loweror higher than the minimum value during an overload situation. In oneimplementation, the system 100 can be provisioned such that the sum ofthe minimum IOPS across all clients is such that the system 100 cansustain the minimum IOPS value for all clients at a given time. In thissituation, each client should be able to perform at or above its minimumIOPS value. The system 100, however, can also be provisioned such thatthe sum of the minimum IOPS across all clients is such that the system100 cannot sustain the minimum IOPS for all clients. In this case, ifthe system becomes overloaded through the use of all clients, theclient's realized IOPS can be less than the client's minimum IOPS value.In failure situations, the system may also throttle users such thattheir realized IOPS are less than their minimum IOPS value. A maximumIOPS parameter is the maximum sustained IOPS value over an extendedperiod of time. The max burst IOPS parameter is the maximum IOPS valuethat a client can “burst” above the maximum IOPS parameter for a shortperiod of time based upon credits. In one implementation, credits for aclient are accrued when the client is operating under their respectivemaximum IOPS parameter. Accordingly, a client will only be able to usethe system in accordance with their respective maximum IOPS and maximumburst IOPS parameters. For example, a single client will not be able touse the system's full resources, even if they are available, but rather,is bounded by their respective maximum IOPS and maximum burst IOPSparameters.

As noted above, client QoS parameters can be changed at any time by theclient or an administrator. FIG. 2 depicts a user interface 200 forsetting client QoS in accordance with one illustrative implementation.The user interface 200 can include inputs that are used to changevarious QoS parameters. For example, slide bars 202 and/or text boxes204 can be used to adjust QoS parameters. As noted above in oneimplementation, client QoS parameters include a minimum IOPS, a maximumIOPS, and a maximum burst IOPS. Each of these parameters can be adjustedwith inputs, e.g., slide bars and/or text boxes. In addition, the IOPSfor different size IO operations can be shown. In the user interface200, the QoS parameters associated with 4 k sized IO operations arechanged. When any performance parameter is changed, the correspondingIOPS for different sized IO operations are automatically adjusted. Forexample, when the burst parameter is changed, IOPS values 206 areautomatically adjusted. The updated values can be based upon aperformance curve as described in greater detail below. Once the QoSparameters have been set, activating a save changes button 208 updatesthe client's QoS parameters. As described below, the target performancemanager 402 can use the updated QoS parameters, such that the updatedQoS parameters take effect immediately. The updated QoS parameters takeeffect without requiring any user data to be moved in the system.

Performance Management

FIG. 3 depicts a simplified flowchart 300 of a method of performingperformance management according to one implementation. Additional,fewer, or different operations of the method 300 may be performed,depending on the particular embodiment. The method 300 can beimplemented on a computing device. In one implementation, the method 300is encoded on a computer-readable medium that contains instructionsthat, when executed by a computing device, cause the computing device toperform operations of the method 300.

At 302, performance manager 114 determines a client load based on one ormore performance metrics. For example, performance manager 114 maycalculate a client's load based on different performance metrics, suchas IOPS, bandwidth, and latency. The metrics may be historical metricsand/or current performance metrics. Historical performance may measureprevious performance for an amount of time, such as the last week ofperformance metrics. Current performance may be real-time performancemetrics. Using these performance metrics, e.g., system metrics and/orclient metrics, a load value is calculated. Example load values aredescribed in greater detail below.

At 303, performance manager 114 gathers information about health of thecluster. The health of the cluster may be information that can quantifyperformance of the cluster, such as a load value. The cluster healthinformation may be gathered from different parts of system 100, and mayinclude health in many different aspects of system 100, such as systemmetrics and/or client metrics. In addition and as described in greaterdetail below, cluster health information can be calculated as a loadvalue from the client and/or system metrics. As described in greaterdetail below, the health information may not be cluster-wide, but mayinclude information that is local to the volume server 122 that isperforming the performance management. The cluster health may beaffected; for example, if there is a cluster data rebuild occurring,total performance of the cluster may drop. Also, when data discarding,adding or removing of nodes, adding or removing of volumes, powerfailures, used space, or other events affecting performance areoccurring, performance manager 114 gathers this information from thecluster.

At 304, performance manager 114 determines a target performance value.For example, based on the load values and client quality of serviceparameters, a target performance value is determined. As will bedescribed in more detail below, the target performance value may bebased on different criteria, such as load values, client metrics, systemmetrics, and quality of service parameters. The target performance valueis the value at which performance manager 114 would like client 108 tooperate. For example, the target performance may be 110 IOPS.

At 306, performance manager 114 adjusts the performance of client 108.For example, the future client performance may be adjusted toward thetarget performance value. If IOPS are being measured as the performancemetric, the number of IOPS a client 108 performs over a period of timemay be adjusted to the target performance value. For example, latencycan be introduced or removed to allow the number of IOPS that a clientcan perform to fluctuate. In one example, if the number of IOPS in theprevious client performance is 80 and the target performance value is110 IOPS, then the performance of the client is adjusted to allow client108 to perform more IOPS such that the client's performance moves towardperforming 110 IOPS.

Traditional provisioning systems attempt to achieve a quality of serviceby placing a client's data on a system that should provide the clientwith the requested quality of service. A client requesting a change totheir quality of service, therefore, can require that the client's databe moved from one system to another system. For example, a client thatwants to greatly increase its quality of service may need to be moved toa more robust system to ensure the increased quality of service. Unlikethe traditional provisioning systems, the performance manager candynamically adjust quality of service for specific clients withoutmoving the client's data to another cluster. Accordingly, quality ofservice for a client can be adjusted instantly, and a client can changeQoS parameters without requiring manual intervention for those QoSparameters to take effect. This feature allows the client to schedulechanges to their QoS parameters. For example, if a client performsbackups on the first Sunday of every month from 2:00 am-4:00 am, theycould have their QoS parameters automatically change just prior to thestart of the backup and change back after the backup finishes. Thisaspect allows a client the flexibility to schedule changes to their QoSparameters based upon the client's need. As another example, the clientcan be presented with a turbo button. When selected, the turbo buttonincreases the client's QoS parameters by some factor, e.g., 3, 4, 5,etc., or to some large amount. Clients could use this feature if theirdata needs were suddenly increased, such as when a client's website isexperiencing a high number of visitors. The client could then unselectthe turbo button to return to their original QoS parameters. Clientscould be charged for how long they use the turbo button features. Inanother implementation, the turbo button remains in effect for apredetermined time before the client's original QoS parameters arereset.

In addition to the above examples, clients and/or administrators can setclient QoS parameters based upon various conditions. In addition, asnoted above client QoS parameters are not limited to IOPS. In differentimplementations, client QoS parameters can be bandwidth, latency, etc.According to different embodiments, the storage system may be configuredor designed to allow service providers, clients, administrators and/orusers, to selectively and dynamically configure and/or define differenttypes of QoS and provisioning rules which, for example, may be based onvarious different combinations of QoS parameters and/or provisioning/QoStarget types, as desired by a given user or client.

According to different embodiments, examples of client QoS parametersmay include, but are not limited to, one or more of the following (orcombinations there:

IOPS;

Bandwidth;

Write Latency;

Read Latency;

Write buffer queue depth;

I/O Size (e.g., amount of bytes accessed per second);

I/O Type (e.g., Read I/Os, Write I/Os, etc.);

Data Properties such as, for example, Workload Type (e.g., Sequential,Random); Dedupe-ability; Compressability; Data Content; Data Type (e.g.,text, video, images, audio, etc.);

etc.

According to different embodiments, examples of various provisioning/QoStarget types may include, but are not limited to, one or more of thefollowing (or combinations thereof):

Service or group of Services;

Client or group of Clients;

Connection (e.g. Client connection);

Volume, or group of volumes;

Node or group of nodes;

Account/Client;

User;

iSCSI Session;

Time segment;

Read IOPS amount;

Write IOPS amount;

Application Type;

Application Priority;

Region of Volume (e.g., Subset of LBAs);

Volume Session(s);

I/O size;

Data Property type;

etc.

FIG. 8 shows an example QoS Interface GUI 800 which may be configured ordesigned to enable service providers, users, and/or other entities todynamically define and/or create different performance classes of useand/or to define performance/QoS related customizations in the storagesystem. In at least one embodiment, the QoS Interface GUI may beconfigured or designed to allow service providers, users, and/or otherentities dynamically switch between the different performance classes ofuse, allowing such clients to dynamically change their performancesettings on the fly (e.g., in real-time).

For example, according to various embodiments, a service provider maydynamically define and/or create different performance classes of use inthe storage system, may allow clients to dynamically switch between thedifferent performance classes of use, allowing such clients todynamically modify or change their performance settings on the fly(e.g., in real-time). In at least one embodiment, the storage system isconfigured or designed to immediately implement the specified changesfor the specified provisioning/QoS Targets, and without requiring theclient's storage volume to be taken off-line to implement theperformance/QoS modifications. In at least one embodiment, the differentperformance classes of use may each have associated therewith arespective set of QoS and/or provisioning rules (e.g., 810) which, forexample, may be based on various different combinations of QoSparameters and/or provisioning/QoS target types.

The above process for performing performance management may be performedcontinuously over periods of time. For example, a period of 500milliseconds is used to evaluate whether performance should be adjusted.As will be described in more detail below, client 108 may be locked outof performing IOPS for a certain amount of time each period to reduce orincrease the number of IOPS being performed.

Examples of different types of conditions, criteria and/or otherinformation which may be used to configure the QoS Interface GUI of FIG.8 may include, but are not limited to, one or more of the following (orcombinations thereof):

Example Boundary Conditions (e.g., 824)

LOAD(Service); Date LOAD(Read); Read IOPS LOAD(Write); Write IOPSLOAD(Write_Buffer); Application Type LOAD(Client-Read); ApplicationPriority LOAD(Client-Write); Region of Volume LOAD(Client); LBA IDLOAD(Cluster); Volume Session ID LOAD(System) Connection ID WriteLatency; I/O size Read Latency; I/O Type Write buffer queue depth;Workload Type LOAD(Client); Dedupe-ability Volume ID CompressabilityGroup ID Data Content Account ID Data Type Client ID Data PropertiesUser ID Detectable Condition and/or Event iSCSI Session ID Etc. Time

Example QoS Parameters(e.g., 842)

MAX IOPS MAX Read I/O MIN IOPS MIN Read I/O BURST IOPS BURST Read I/OMAX Bandwidth MAX Write I/O MIN Bandwidth MIN Write I/O BURST BandwidthBURST Write I/O MAX Latency I/O Type MIN Latency Workload Type BURSTLatency Dedupe-ability MAX I/O Size Compressability MIN I/O Size DataContent BURST I/O Size Data Type I/O Type Billing Amount

Example Provisioning/QoS Targets (e.g., 844)

Cluster ID Application Type Service ID Application Priority Client IDRegion of Volume Connection ID LBA ID Node ID Volume Session ID VolumeID Connection ID Group ID I/O size Account ID I/O Type Client IDWorkload Type User ID Dedupe-ability iSCSI Session ID CompressabilityTime Data Content Date Data Type Read IOPS Data Properties Write IOPSEtc.

Example Operators (e.g., 826, 846)

Equal To Not Equal To Less Than Contains Greater Than Does Not ContainLess Than or Equal To Matches Greater Than or Equal To RegularExpression(s) Within Range of

Example Threshold Values (e.g., 828, 848)

Alpha-numeric value(s) Random Type Numeric value(s) Text Type NumericRange(s) Video Type Numeric value per Time Interval value Audio Type(e.g., 5000 IOPS/sec) Image Type Sequential Type Performance Class ofUse Value

Example Boolean Operators (e.g., 825, 845)

AND NAND OR NOR XOR XNOR NOT EXCEPT

The following example scenarios help to illustrate the various featuresand functionalities enabled by the QoS Interface GUI 800, and help toillustrate the performance/QoS related provisioning features of thestorage system:

Example A—Configuring/provisioning the storage system to automaticallyand/or dynamically increase storage performance to enable a backup to gofaster during a specified window of time. For example, in oneembodiment, the speed of a volume backup operation may be automaticallyand dynamically increased during a specified time interval by causing aMAX IOPS value and/or MIN IOPS value to be automatically and dynamicallyincreased during that particular time interval.

Example B—Configuring/provisioning the storage system to automaticallyand/or dynamically enable a selected initiator to perform fastersequential IOs from 10 pm to Midnight.

Example C—Configuring/provisioning the storage system to automaticallyand/or dynamically enable a selected application to have increased I/Ostorage performance.

Example D—Configuring/provisioning the storage system to automaticallyand/or dynamically enable a selected group of clients to have theirrespective MAX, MIN and BURST IOPS double on selected days/dates of eachmonth.

Example E—Configuring/provisioning the storage system to present aclient or user with a “Turbo Boost” interface which includes a virtualTurbo Button. Client may elect to manually activate the Turbo Button(e.g., on the fly or in real-time) to thereby cause the storage systemto automatically and dynamically increase the level of performanceprovisioned for that Client. For example, in one embodiment, clientactivation of the Turbo Button may cause the storage system toautomatically and dynamically increase the client's provisionedperformance by a factor of 3× for one hour. In at least one embodiment,the dynamic increase in provisioned performance may automatically ceaseafter a predetermined time interval. In at least one embodiment, thestorage system may be configured or designed to charge the client anincreased billing amount for use of the Turbo Boost service/feature.

Example F—Configuring/provisioning the storage system to automaticallyand/or dynamically charge an additional fee or billing amount fordynamically providing increased storage array performance (e.g., toallow a faster backup) to go faster at a particular time.

Example G—Configuring/provisioning the storage system to automaticallyand/or dynamically charge an additional fee or billing amount for IOPSand/or I/O access of the storage system which exceeds minimum thresholdvalue(s) during one or more designated time intervals.

Performance manager 114 may use different ways of adjusting performance.FIG. 4 depicts a more detailed example of adjusting performance usingperformance manager 114 according to one implementation. A targetperformance manager 402 determines a target performance value. In oneimplementation, target performance manager 402 uses the client's QoSparameters, system metrics, and client metrics to determine the targetperformance value. As will be described in greater detail below, systemmetrics and client metrics can be used to determine the system load andclient load. As an example, client load can be measured based on aclient metrics, such as in IOPS, bytes, or latency in milliseconds.

In one implementation, system metrics are data that quantifies thecurrent load of the cluster. As will be described in greater detailbelow, various system load values can be calculated based upon thesystem metrics. The load values can be normalized measures of systemload. For example, different load values can be compared to one another,even if the load values use different metrics in their calculations. Asan example, system load can be expressed in a percentage based on thecurrent load of the cluster. In one example, a cluster that isoverloaded with processing requests may have a lower value than when thesystem is not overloaded. In another implementation, the targetperformance manger 402 receives calculated load values as input, ratherthan system and/or client metrics.

The target performance manager 402 can read the client QoS parameters,relevant system metrics, and relevant client metrics. These values canbe used to determine the target performance value for client 108. TheQoS parameters may also be dynamically adjusted during runtime by theadministrator or the client as described above, such as when a higherlevel of performance is desired (e.g., the customer paid for a higherlevel of performance). The calculation of the target performance valueis explained in greater detail below.

In one implementation, the target performance manager 402 outputs thetarget performance value to a proportion-integral-derivative (PID)controller block 404. PID controller block 404 may include a number ofPID controllers for different performance metrics. Although PIDcontrollers are described, other controllers may be used to control theperformance of clients 108. In one example, PID controller block 404includes PID controllers for IOPS, bandwidth, and latency. Targetperformance manager 402 outputs different target performance values forthe performance metrics into the applicable PID controllers. The PIDcontrollers also receive information about previous and/or currentclient performance and the target performance value. For example, thePID controllers can receive client metrics, system metrics, and/or loadvalues, that correspond with the target performance value. The PIDcontroller can then determine a client performance adjustment value. Forexample, a PID controller is configured to take feedback of previousclient performance and determine a value to cause a system to movetoward the target performance value. For example, a PID can cause variedamounts of pressure to be applied, where pressure in this case causesclient 108 to slow down, speed up or stay the same in performing IOPS.As an example, if the target performance value is 110 IOPS and client108 has been operating at 90 IOPS, then the client performanceadjustment value is output, which by being applied to the client 108should increase the number of IOPS being performed.

In one implementation, PID controller block 404 outputs a performanceadjustment value. As an example, the performance adjustment value can bea pressure value that indicates an amount of time that the client islocked out performing IO operations within the storage system. This lockout time will cause client performance to move toward the targetperformance value. For example, a time in milliseconds is output that isused to determine how long to lock a client 108 out of a volume. Lockinga client out of performing IO operations artificially injects latencyinto the client's IO operations. In another of implementations, theperformance adjustment value can be a number of IO operations that theclient can perform in a period of time. If the client attempts to domore IO operations, the client can be locked out of doing those IOoperations until a subsequent period of time. Locking client 108 out ofthe volume for different times changes the number of IOPS performed byclient 108. For example, locking client 108 out of the volume forshorter periods of time increases the number of IOPS that can beperformed by client 108 during that period.

A performance controller 406 receives the performance adjustment valueand outputs a client control signal to control the performance of client108. For example, the amount of lockout may be calculated and appliedevery half second. In one implementation, clients 108 are locked out byclosing and opening a command window, such as an Internet small computersystem interface (iSCSI) command window. Closing the command window doesnot allow a client 108 to issue access requests to a volume and openingthe command window allows a client 108 to issue access requests to thevolume. Locking clients 108 out of a volume may adjust the number ofIOPS, bandwidth, or latency for client 108. For example, if a client 108is locked out of a volume every 50 milliseconds of every 500milliseconds as compared to being locked out of the volume for 450milliseconds of every 500 milliseconds, the client may issue more IOPS.For a bandwidth example, if bandwidth is constrained, then client 108 islocked out of a volume for a longer period of time to increase availablebandwidth. In another implementation, the amount of data that is beingserviced at a time is modified, either to zero or some number, to affectthe performance at which the system services that client's IO.

As described above, IOPS are metrics that can be used to manageperformance of a client. IOPS include both write IOPS and read IOPS.Individual input/output operations do not have a set size. That is, aninput operation can be writing 64 k of data to a drive, while anotherinput operation can be writing 4 k of data to the drive. Accordingly,capturing the raw number of input/output operations over a period oftime does not necessarily capture how expensive the IO operationactually is. To account for this situation, an input/output operationcan be normalized based upon the size of the I/O operation. This featureallows for consistent treatment of IOPS, regardless of each operation'ssize of the data. This normalization can be achieved using a performancecurve. FIG. 5 depicts a performance curve 500 comparing the size ofinput/output operations with system load in accordance with anillustrative implementation. Line 504 indicates the system at full load,while line 502 indicates the load of the system for IO operations ofdiffering sizes. The performance curve can be determined based uponempirical data of the system 100. The performance curve allows IOPS ofdifferent sizes to be compared and to normalize IOPS of different sizes.For example, an IOP of size 32 k is roughly five times more costly thana 4 k IOP. That is, the number of IOPS of size 32 k to achieve 100% loadof a system is roughly 20% of the number of IOPS of size 4 k. This isbecause larger block sizes have a discount of doing IP and not having toprocess smaller blocks of data. In various implementations, this curvecan be used as a factor in deciding a client's target performance value.For example, if the target performance value for a client is determinedto be 1,000 IOPS, this number can be changed based upon the average sizeof IOs the client has done in the past. As an example, if a client'saverage IO size is 4 k, the client's target performance value can remainat 1,000 IOPS. However, if the client's average IO size is determined tobe 32 k, the client's target performance value can be reduced to 200IOPS, e.g., 1,000*0.2. The 200 IOPS of size 32 k is roughly equivalentto 1,000 IOPS of size 4 k.

In determining a target performance value, the target performancemanager 402 uses a client's QoS parameters to determine the targetperformance value for a client. In one implementation, an overloadcondition is detected and all clients are throttled in a consistentmanner. For example, if the system load is determined to be at 20%, allclients may be throttled such that their target performance value is setto 90% of their maximum IOPS setting. If the system load increases to50%, all clients can be throttled based upon setting their targetperformance value to 40% of their maximum IOPS setting. Additionalexamples of how overload conditions are determined are provided below.

Clients do not have to be throttled in a similar manner. For example,clients can belong to different classes of uses. In one implementation,classes of uses can be implemented simply by setting the QoS parametersof different clients differently. For example, a premium class of usecould have higher QoS parameters, e.g., min IOPS, max IOPS, and burstIOPS, values compared to a normal class of use. In anotherimplementation, the class of use can be taken into account whencalculating the target performance value. For example, taking twodifferent classes, one class could be throttled less than the otherclass. Using the example scenario above, clients belonging to the firstclass could be throttled 80% of their maximum IOPS value when the systemload reaches 20%. The second class of clients, however, may not bethrottled at all or by a different amount, such as 95% of their maximumIOPS value.

In another implementation, the difference between a client's minimumIOPS and maximum IOPS can be used to determine how much to throttle aparticular client. For example, a client with a large difference can bethrottled more than a client whose difference is small. In oneimplementation, the difference between the client's maximum IOPS andminimum IOPS is used to calculate a factor that is applied to calculatethe target performance value. In this implementation, the factor can bedetermined as the IOPS difference divided by some predetermined IOPSamount, such as 5,000 IOPS. In this example, a client whose differencebetween their maximum IOPS and their minimum IOPS was 10,000, would bethrottled twice as much as a client whose IOPS difference was 5,000.Clients of the system can be billed different amounts based upon theirclass. Accordingly, clients could pay more to be throttled later and/orless than other classes of clients.

In another implementation, throttling of clients can be based upon theclient's use of the system. In this implementation, the targetperformance manager 402 can review system metrics to determine whatmetrics are currently overloaded. Next, the client metrics can beanalyzed to determine if that client is contributing to an overloadedsystem value. For example, the target performance manager 402 candetermine that the system is overloaded when the cluster's write latencyis overloaded. The read/write IOPS ratio for a client can be used todetermine if a particular client is having a greater impact on theoverload condition. Continuing this example, a client whose read/writeIOPS ratio was such that the client was doing three times more writesthan reads and was doing 1,500 writes would be determined to benegatively impacting the performance of the cluster. Accordingly, thetarget performance manager 402 could significantly throttle this client.In one implementation, this feature can be done by calculating a factorbased upon the read/write IOPS ratio. This factor could be applied whencalculating the target performance value, such that the example clientabove would be throttled more than a client whose read/write IOPS ratiowas high. In this example, a high read/write IOPS ratio indicates thatthe client is doing more reads than writes. The factor can also be basedupon the number of IOPS that each client is doing. In addition, thenumber of IOPS for a particular client can be compared to the number ofIOPS for the cluster, such that an indication of how heavily aparticular client is using the cluster can be determined. Using thisinformation, the target performance manager can calculate another factorthan can be used to scale the target performance value based upon howmuch a client is using the system compared to all other clients.

FIG. 6 depicts a simplified flowchart of a method 600 of performingperformance management that matches an overloaded system metric with aclient metric in accordance with one illustrative implementation.Additional, fewer, or different operations of the method 600 may beperformed, depending on the particular embodiment. The method 600 can beimplemented on a computing device. In one implementation, the method 600is encoded on a computer-readable medium that contains instructionsthat, when executed by a computing device, cause the computing device toperform operations of the method 600.

In an operation 602, client metrics can be determined. For example, aperformance manager 114 can determine client metrics, as describedabove, for a preceding period of time, e.g., 100 ms, 1 s, 10 s, etc. Inan operation 604, system metrics can be determined. For example, theperformance manager 114 or another process can determine system metricsas described above. In one implementation, the client metrics and/orsystem metrics are used to calculate one or more load values. Thecalculation of load values is described in greater detail below. In anoperation 606, the target performance manager 402 can then determine ifthe system is overloaded in way based upon various load values. Forexample, the target performance manager 402 can determine if a system isoverloaded by comparing system load values with correspondingthresholds. Any load value above its corresponding threshold indicatesan overload condition. In one implementation, the system load values areanalyzed in a prioritized order and the first overloaded load value isused to determine how to throttle clients.

In an operation 608, one or more corresponding client metrics associatedwith the overloaded load value are determined. For example, if theoverloaded system load is the number of read operations, the client'snumber of read operations can be used as the associated client metric.The client's metric does not have to be the same as the overloadedsystem metric. As another example, if the overloaded system load is readlatency, the corresponding client metrics can be the ratio of read towrite IO operations and the total number of read operations for aclient. In an operation 610, a client-specific factor is determinedbased upon the client metric associated with the overloaded system loadvalue. In the first example above, the factor can be the number of theclient's read operations divided by the total number of read operationsof the cluster. The client factor, therefore, would be relative to howmuch the client is contributing to the system load value. Clients thatwere dong a relatively larger number of reads would have a greaterclient metric compared with a client that was doing a relatively smallernumber of reads.

In an operation 612, the client-specific factor is used to calculate thetarget performance value for the client. In one implementation, aninitial target performance value can be calculated and then multipliedby the client specific factor. In another implementation, a clusterreduction value is determined and this value is multiplied by the clientspecific factor. Continuing the example above, the cluster reductionvalue can be the number of read IOPS that should be throttled. Comparedto throttling each client equally based upon the cluster reductionvalue, using the client-specific factor results in the same number ofread IOPS that are throttled, but clients who have a large number ofread IO operations are throttled more than clients who have a smallernumber of read IO operations. Using client-specific factors helps thetarget performance manager 402 control the throttling of clients to helpensure that the throttling is effective. For example, if client-specificfactors were not used and throttling was applied equally across allclients, a client whose use of the system was not contributing to thesystem's overloading would be unnecessarily throttled. Worse, thethrottling of all of the clients might not be as effective since thethrottling of clients who did not need to be throttled would not helpease the overloading condition, which could result in even morethrottling being applied to clients.

In an operation 614, the performance manager 114 can adjust theperformance of client 108. For example, the client's use of the systemcan be throttled as described above.

Using the above system, clients 108 may be offered performanceguarantees based on performance metrics, such as IOPS. For example,given that system 100 can process a total number of IOPS, the totalnumber may be divided among different clients 108 in terms of a numberof IOPS within the total amount. The IOPS are allocated using the min,max, and burst. If it is more than the total then possible, theadministrator is notified that too many IOPS are being guaranteed andinstructed to either add more performance capacity or change the IOPguarantees. This notification may be before a capacity threshold isreached (e.g., full capacity or a pre-defined threshold below fullcapacity). The notification can be sent before the capacity is reachedbecause client performance is characterized in terms of IOPS and theadministrator can be alerted that performance is overprovisioned by Nnumber of IOPS. For example, clients 108 may be guaranteed to beoperating between a minimum and maximum number of IOPS over time (withbursts above the maximum at certain times). Performance manager 114 canguarantee performance within these QoS parameters using the abovesystem. Because load is evenly distributed, hot spots will not occur andsystem 100 may operate around the total amount of IOPS regularly. Thus,without hot spot problems and with system 100 being able to provide thetotal amount of IOPS regularly, performance may be guaranteed forclients 108 as the number of IOPS performed by clients 108 are adjustedwithin the total to make sure each client is operating within the QoSparameters for each given client 108. Since each client's effect on aglobal pool of performance is measured and predictable, theadministrator can consider the entire cluster's performance as a pool ofperformance as opposed to individual nodes, each with its ownperformance limits. This feature allows the cluster to accuratelycharacterize its performance and guarantee its ability to deliverperformance among all of its volumes.

Accordingly, performance management is provided based on the distributeddata architecture. Because data is evenly distributed across all drivesin the cluster, the load of each individual volume is also equal acrossevery single drive in storage system 100. This feature may remove hotspots and allow performance management to be accurate and fairlyprovisioned and to guarantee an entire cluster performance forindividual volumes.

Load Value Calculations

Load values can be used to determine if a client should be throttled tohelp ensure QoS among all clients. Various load values can be calculatedbased upon one or more system metric and/or client metric. As anexample, a load value can be calculated that corresponds to a client'sdata read latency. When calculating a load value that corresponds with aclient, how the client's data is managed on the storage system becomesimportant.

FIG. 9 shows a portion of a storage system in accordance with oneillustrative implementation. In the specific example embodiment of FIG.9, the storage system is shown to include a cluster 910 of nodes (912,914, 916, and 918). According to different embodiments, each node mayinclude one or more storage devices such as, for example, one or moresolid state drives (SSDs). In the example embodiment of FIG. 9, it isassumed for purposes of illustration that three different clients (e.g.,Client A 902, Client B 904, and Client C 906) are each actively engagedin the reading/writing of data from/to storage cluster 910.

Additionally, as illustrated in the example embodiment of FIG. 9, eachnode may have associated therewith one or more services (e.g., ServicesA-H), wherein each service may be configured or designed to handle aparticular set of functions and/or tasks. For example, as illustrated inthe example embodiment of FIG. 9: Services A and B may be associatedwith (and/or may be handled by) Node 1 (912); Services C and D may beassociated with (and/or may be handled by) Node 2 (914); Service E maybe associated with (and/or may be handled by) Node 3 (916); Services F,G, H may be associated with (and/or may be handled by) Node 4 (918). Inat least one embodiment, one or more of the services may be configuredor designed to implement a slice server. A slice server can also bedescribed as providing slice service functionality.

Additionally, according to different embodiments, a given service mayhave associated therewith at least one primary role and further may haveassociated therewith one or more secondary roles. For example, in theexample embodiment of FIG. 9, it is assumed that Service A has beenconfigured or designed to include at least the following functionality:(1) a primary role of Service A functions as the primary slice servicefor Client A, and (2) a secondary role of Service A handles thedata/metadata replication tasks (e.g., slice service replication tasks)relating to Client A, which, in this example involves replicating ClientA's write requests (and/or other slice-related metadata for Client A) toService C. Thus, for example, in one embodiment, write requestsinitiated from Client A may be received at Service A 902 a, and inresponse, Service A may perform and/or initiate one or more of thefollowing operations (or combinations thereof):

-   -   process the write request at Service A's slice server, which,        for example, may include generating and storing related metadata        at Service A's slice server;    -   (if needed) cause the data (of the write request) to be saved in        a first location of block storage (e.g., managed by Service A);    -   forward (902 b) the write request (and/or associated        data/metadata) to Service C for replication.

In at least one embodiment, when Service C receives a copy of the ClientA write request, it may respond by processing the write request atService C's slice server, and (if needed) causing the data (of the writerequest) to be saved in a second location of block storage (e.g.,managed by Service C) for replication or redundancy purposes. In atleast one embodiment, the first and second locations of block storagemay each reside at different physical nodes. Similarly Service A's sliceserver and Service C's slice server may each be implemented at differentphysical nodes.

Accordingly, in the example embodiment of FIG. 9, the processing of aClient A write request may involve two distinct block storage writeoperations—one initiated by Service A (the primary Service) and anotherinitiated by Service C (the redundant Service). On the other hand, theprocessing of a Client A read request may only be handled by Service A(e.g., under normal conditions) since Service A is without involvingService C) since Service A is able to handle the read request withoutnecessarily involving Service C.

For purposes of illustration, in the example embodiment of FIG. 9, it isalso assumed that Service E has been configured or designed to includeat least the following functionality: (1) a primary role of Service Efunctions as the primary slice service for Client B, and (2) a secondaryrole of Service E handles the data and/or metadata replication tasks(e.g., slice service replication tasks) relating to Client B, which, inthis example involves replicating Client B's write requests (and/orother Slice-related metadata for Client B) to Service D. Thus, forexample, in one embodiment, write requests initiated from Client B maybe received at Service E 904 a, and in response, Service E may performand/or initiate one or more of the following operations (or combinationsthereof):

-   -   process the write request at Service E's slice server, which,        for example, may include generating and storing related metadata        at Service E's slice server;    -   (if needed) cause the data (of the write request) to be saved in        a first location of block storage (e.g., managed by Service E);    -   forward (904 b) the write request (and/or associated        data/metadata) to Service D for replication.

In at least one embodiment, when Service D receives a copy of the ClientB write request, it may respond by processing the write request atService D's slice server, and (if needed) causing the data (of the writerequest) to be saved in a second location of block storage (e.g.,managed by Service D) for replication or redundancy purposes. In atleast one embodiment, the first and second locations of block storagemay each reside at different physical nodes. Similarly Service E's sliceserver and Service D's slice server may each be implemented at differentphysical nodes.

According to different embodiments, it is also possible to implementmultiple replication (e.g., where the data/metadata is replicated at twoor more other locations within the storage system/cluster). For example,as illustrated in the example embodiment of FIG. 9, it is assumed thatService E has been configured or designed to include at least thefollowing functionality: (1) a primary role of Service E functions asthe primary slice service for Client C, (2) a secondary role of ServiceE handles the data and/or metadata replication tasks (e.g., sliceservice replication tasks) relating to Client C, which, in this exampleinvolves replicating Client C's write requests (and/or otherSlice-related metadata for Client C) to Service C; and (3) a secondaryrole of Service E handles the data and/or metadata replication tasks(e.g., slice service replication tasks) relating to Client C, which, inthis example involves replicating Client C's write requests (and/orother Slice-related metadata for Client C) to Service G. Thus, forexample, in one embodiment, write requests initiated from Client C maybe received at Service E 906 a, and in response, Service E may performand/or initiate one or more of the following operations (or combinationsthereof):

-   -   process the write request at Service E's slice server, which,        for example, may include generating and storing related metadata        at Service E's slice server;    -   (if needed) cause the data (of the write request) to be saved in        a first location of block storage (e.g., managed by Service E);    -   forward (906 b) the write request (and/or associated        data/metadata) to Service C for replication;    -   forward (906 c) the write request (and/or associated        data/metadata) to Service G for replication.

In at least one embodiment, when Service C receives a copy of the ClientC write request, it may respond by processing the write request atService C's slice server, and (if needed) causing the data (of the writerequest) to be saved in a second location of block storage (e.g.,managed by Service C) for replication or redundancy purposes. Similarly,In at least one embodiment, when Service G receives a copy of the ClientC write request, it may respond by processing the write request atService G's slice server, and (if needed) causing the data (of the writerequest) to be saved in a third location of block storage (e.g., managedby Service G) for replication or redundancy purposes.

Load Values and Quality of Service (QoS) Analysis

According to different embodiments, the QoS functionality of the storagesystem may use as input various load values determined from systemmetrics and/or client metrics. For example, in one embodiment, thestorage system may be configured or designed to measure, track, and/oranalyze system resources that are used or are impacted for read and/orwrite operations to help determine the degree to which one or moresystem resources may be loaded, stressed and/or overloaded.

In at least one embodiment, different types of metrics can be used tocalculate load values that can be used to express the degree to whichone or more system resources (e.g., nodes, components, services, etc.)are loaded, stressed and/or overloaded. For example, in at least oneembodiment, one or more different types of load values may beautomatically and/or dynamically calculated to express or quantify therelative degrees to which various types system resources may be loaded,stressed and/or overloaded. Examples of various types of load values mayinclude, but are not limited to, one or more of the following (orcombinations thereof):

-   -   LOAD(Service) which, for example, may express the relative        degree or amount of system resource load or stress relating to        an identified Service running at the system. According to        different embodiments, the LOAD(Service) value may be        automatically and/or dynamically calculated (e.g., in real-time)        based, at least partially, on measured amount(s) of read latency        and/or write latency relating to read and/or write operations        associated with the identified Service. In at least one        embodiment where the Service has been assigned to handle        read/write operations from multiple Clients, the LOAD(Service)        value may reflect read latencies and/or write latencies        attributable to read/write operations associated with the        multiple Clients to which the Service has been assigned.    -   LOAD(Read) which, for example, may express the relative degree        or amount of system resource load or stress relating to Read        IOPS. According to different embodiments, the LOAD(Read) value        may be automatically and/or dynamically calculated (e.g., in        real-time) based, at least partially, on measured amount(s) of        system latency relating to Read IOPS. According to different        embodiments, the LOAD(Read) metric may be configured to express        the relative degree or amount of system resource load or stress        relating to Read IOPS which are associated with one or more of        the following (or combinations thereof): an identified Service,        a group of identified Services, an identified Client, an        identified connection (e.g., Client connection), an identified        volume (or portion thereof), an identified group of volumes, an        identified node, an identified group of nodes, and/or other        specifically identified system resources.    -   LOAD(Write) which, for example, may express the relative degree        or amount of system resource load or stress relating to Write        IOPS. According to different embodiments, the LOAD(Write) value        may be automatically and/or dynamically calculated (e.g., in        real-time) based, at least partially, on measured amount(s) of        system latency relating to Write IOPS. According to different        embodiments, the LOAD(Write) metric may be configured to express        the relative degree or amount of system resource load or stress        relating to Write IOPS which are associated with one or more of        the following (or combinations thereof): an identified Service,        a group of identified Services, an identified Client, an        identified connection (e.g., Client connection), an identified        volume (or portion thereof), an identified group of volumes, an        identified node, an identified group of nodes, and/or other        specifically identified system resources.    -   LOAD(Write_Buffer) which, for example, may express the relative        amount of write buffer cache capacity being used. According to        different embodiments, the LOAD(Write_Buffer) value may be        automatically and/or dynamically calculated (e.g., in real-time)        based, at least partially, on the percentage of fullness of the        write buffer cache.    -   LOAD(Client) which, for example, may express the relative degree        or amount of system resource load or stress relating to IO        activities associated with the Service(s) (e.g., primary Service        and secondary Service(s)) which have been assigned to handle        read, write and replication operations for the identified        Client. According to different embodiments, the LOAD(Client)        value may be automatically and/or dynamically calculated (e.g.,        in real-time) based, at least partially, on measured amount(s)        of read latency and/or write latency relating to the Service(s)        which have been assigned to handle read, write and replication        operations for the identified Client.    -   LOAD(Client-Read) which, for example, may express the relative        degree or amount of system resource load or stress relating to        IO activities associated with the Service(s) which have been        assigned to handle read operations for the identified Client.        According to different embodiments, the LOAD(Client-Read) value        may be automatically and/or dynamically calculated (e.g., in        real-time) based, at least partially, on measured amount(s) of        read latency relating to the Service(s) which have been assigned        to handle IO operations for the identified Client.    -   LOAD(Client-Write) which, for example, may express the relative        degree or amount of system resource load or stress relating to        IO activities associated with the Service(s) which have been        assigned to handle Write operations for the identified Client.        According to different embodiments, the LOAD(Client-Write) value        may be automatically and/or dynamically calculated (e.g., in        real-time) based, at least partially, on measured amount(s) of        write latency relating to the Service(s) which have been        assigned to handle IO operations for the identified Client.    -   LOAD(Resource) which, for example, may express the relative        degree or amount of system load or stress relating to the        identified Resource (e.g., cache memory, disk storage space,        cluster storage space, etc.). According to different        embodiments, the LOAD(Resource) value may be automatically        and/or dynamically calculated (e.g., in real-time) (e.g., in        real-time) based, at least partially, on resource        availability/usage characteristics and/or performance        characteristics relating to one or more of the following (or        combinations thereof): cluster level metrics and/or drive level        metrics, read latency, write latency, input/output operations        per second (IOPS), read IOPS, write IOPS, I/O size, write cache        capacity, dedupe-ability, compressibility, total bandwidth, read        bandwidth, write bandwidth, read/write ratio, workload type,        data content, data type, etc. LOAD(System) which, for example,        may express the relative degree or amount of system load or        stress relating to a selected portion of the storage system.    -   LOAD(DSU-Service) which, for example, may express the relative        amount of disk space utilization (DSU) for an identified        Service.    -   LOAD(DSU-Cluster) which, for example, may express the relative        amount of disk space utilization (DSU) for an identified Storage        Cluster.    -   LOAD(Cluster) which, for example, may express the relative        degree or amount of system load or stress relating to an        identified Storage Cluster (e.g., Storage Cluster 910, FIG. 9)

As shown above, a client load value can be calculated based upon boththe read latency and the write latency metrics of the client. Inaddition, separate client load values can be calculated based on readlatency and write latency metrics. In at least one embodiment, one ormore aspects relating to QoS management may be initiated and/orfacilitated by monitoring and differentiating between read-related IOPSand write-related IOPS (e.g., for a given Client, Service, and/or groupof Services). For example, in one embodiment, to facilitate QoSimplementation for read-related operations relative to a given service(e.g., Service A), read latency of the volumes associated with Service Amay be monitored and/or measured. In one embodiment, read latency ofgiven volume may be calculated or determined based on the amount of timeit takes for the system to internally service and complete a data readoperation(s) conducted between the identified service (e.g., sliceservice) and the corresponding block service from which the data isread.

To initiate and/or facilitate QoS implementation for write-relatedoperations relative to a given service (e.g., Service A), write latencyof the volumes associated with Service A may be monitored and/ormeasured. In one embodiment, write latency of given volume may becalculated or determined based on the amount of time it takes for thesystem to internally service and complete the data write operation(s)conducted between the identified service (e.g., slice service) and thecorresponding block service to which the data is written.

In at least one embodiment, to facilitate QoS implementation forwrite-related operations relative to a given Client (e.g., Client A902), write latency of the Services (e.g., Service A, Service C)associated with Client A may be monitored and/or measured. For example,in one embodiment, write latency for a given Client may be calculated ordetermined based on the amount of time it takes for the system tointernally service and complete the associated data write operation(s),which may include, for example: (i) the data write operation(s) handledby the primary slice service (e.g., Service A), and (ii) the data writeoperation(s) handled by each of the secondary (e.g., replication)service(s) (e.g., Service C).

In at least some embodiments, the degree or amount (e.g., percentage) ofavailable write buffer cache capacity (for one or more identified nodes)may also be used or taken into account when performing write latencymeasurements/calculations. For example, for at least some write-relatedoperations, the storage system may utilize one or more write cache(s)(or write buffers) which, for example, may be implemented usingfast-write memory (e.g., such as that associated with battery backedRAM, Marvell™ card, etc.). In at least one embodiment, the storagesystem may monitor the size or amount of queued writes stored on thewrite cache(s), and use this information to proactively manage throttleclients.

For example, in one embodiment, as the load value associated with theamount of data in a given write cache approaches or exceeds predefinedthreshold limits, the storage system automatically and/or dynamicallyidentify and/or implement appropriate procedures to help maintain QoSstandards such as, for example, by applying back pressure duringconditions when it is detected or determined that the data flushingprocess (e.g., from slice service write cache to block storage) cannotkeep up with incoming client writes. In some embodiments, the system mayapply back pressure only to a subset of nodes and/or volumes which havebeen identified as having write caches which meet or exceed predefinedthreshold limits.

According to different embodiments, various examples of procedures whichmay be automatically and/or dynamically initiated and/or implemented bythe storage system may include, but are not limited to, one or more ofthe following (or combinations thereof):

-   -   Temporarily throttling read and write IOPS for one or more        selected services, nodes, volumes, clients, and/or connections;    -   Temporarily throttling read-related IOPS for one or more        selected services, nodes, volumes, clients, and/or connections;    -   Temporarily throttling write-related IOPS for one or more        selected services, nodes, volumes, clients, and/or connections;    -   Deferring internal message requests between one or more selected        services, nodes, volumes, clients, and/or connections;    -   and/or other types of actions/activities which may help reduce        or alleviate the relative degree or amount of system resource        load or stress.

Example Load Calculations

According to different embodiments, various types of techniques and/orcomputer-implemented algorithms may be used for dynamically calculatingdesired LOAD values. By way of illustration, several different exampleembodiments of LOAD calculation techniques are described below withreference to the example system embodiment illustrated in FIG. 9.

Example LOAD Calculation Technique A

In one embodiment, referring to the example system embodimentillustrated in FIG. 9, respective LOAD(Client) values may beautomatically and/or dynamically calculated according to:

LOAD(Client A)=a*LOAD(Service A)+b*LOAD(Service C);

LOAD(Client B)=c*LOAD(Service E)+d*LOAD(Service D);

LOAD(Client C)=e*LOAD(Service E)+f*LOAD(Service C)+g*LOAD(Service G);

where: a, b, c are weighted variables (e.g., weighted coefficients) eachhaving a respective value between 0 and 1; and where: a+b=1, c+d=1, ande+g+f=1.

In at least one embodiment, the value of coefficients may beautomatically and/or dynamically adjusted (e.g., in real-time) based,for example, on measured percentages of Read/Write workloads.

In one embodiment, referring to the example system embodimentillustrated in FIG. 9, LOAD(Service) value(s) for an identified service(Service_ID) may be automatically and/or dynamically calculatedaccording to:

LOAD(Service_ID) = h * LOAD(Read@Service_ID) + j * LOAD(Write@Service_ID) + k * LOAD(Write  Buffer@Service_ID) + m * LOAD(DSU − Service_ID)

where:

-   -   h, j, k, m are weighted variables (e.g., weighted coefficients)        each having a respective value between 0 and 1; and where:        h+j+k+m=1;    -   LOAD(Read@Service_ID) represents a normalized value (e.g.,        between 0-1) which expresses the relative degree or amount of        system resource load/stress associated with read IOPS which are        handled by the Service identified by Service_ID;    -   LOAD(Write@Service_ID) represents a normalized value (e.g.,        between 0-1) which expresses the relative degree or amount of        system resource load/stress associated with write IOPS which are        handled by the Service identified by Service_ID;    -   LOAD(Write_Buffer@Service_ID) represents a normalized value        (e.g., between 0-1) which expresses the relative size or amount        of queued write requests which are queued on the write cache of        the node which is assigned for use by the Service identified by        Service_ID.;    -   LOAD(DSU-Service_ID) represents a normalized value (e.g.,        between 0-1) which expresses the relative amount of disk space        utilization (DSU) for the Service identified by Service_ID.

In at least one embodiment where the Service has been assigned to handleread/write operations from multiple Clients, the LOAD(Read) value mayreflect read latencies attributable to read operations associated withthe multiple Clients to which the Service has been assigned. Similarly,where the Service has been assigned to handle read/write operations frommultiple Clients, the LOAD(Write) value may reflect write latenciesattributable to write operations associated with the multiple Clients towhich the Service has been assigned.

Example LOAD Calculation Technique B

In another embodiment, a LOAD(Client) value for a given client may beautomatically and/or dynamically determined by identifying and selectinga relatively highest value from a set of values which, for example, mayinclude LOAD(client-read) and LOAD(client-write).

Thus, for example, referring to the example system embodimentillustrated in FIG. 9, the LOAD(Client A) value may be automaticallyand/or dynamically calculated according to:

LOAD(Client A)=MAX VALUE {(LOAD(Read@Service A), LOAD(Write@(Service A),LOAD(Write@Service C)}

where:

-   -   MAX_VALUE {x,y,z} represents a function which returns a        relatively highest value selected from the set {x,y,z};    -   LOAD(Read@Service A) represents a normalized value (e.g.,        between 0-1) which expresses the relative degree or amount of        system resource load/stress associated with read IOPS which are        handled by Service A;    -   LOAD(Write@(Service A) represents a normalized value (e.g.,        between 0-1) which expresses the relative degree or amount of        system resource load/stress associated with write IOPS which are        handled by Service A;    -   LOAD(Write@Service C) represents a normalized value (e.g.,        between 0-1) which expresses the relative degree or amount of        system resource load/stress associated with write IOPS which are        handled by Service C.

Similarly, the respective LOAD(Client B) and LOAD(Client C) values mayeach be automatically and/or dynamically calculated according to:

LOAD(Client B)=MAX_VALUE {(LOAD(Read@Service E), LOAD(Write@(Service E),LOAD(Write@Service D)}

LOAD(Client C)=MAX_VALUE {(LOAD(Read@Service E), LOAD(Write@(Service E),LOAD(Write@Service C), LOAD(Write@Service G)}.

Load Value Data Structures

FIGS. 10-12 illustrate example embodiments of different types of dataand data structures which may be used to facilitate read, write, andreplication functionality within the storage system. In at least oneembodiment, a separate instance of one or more of the data structures ofFIGS. 10-12 may be associated with each respective Service which isrunning within the storage cluster (e.g., 910) and instantiated andupdated at the same physical node where it's respective Service isinstantiated. According to different embodiments, the storage system maybe configured or designed to periodically and dynamically generate,populate, and update the various data structures illustrated in FIGS.10-12.

FIG. 10 illustrates a specific example embodiment of a LOAD-Service datastructure 1000. In at least one embodiment, the LOAD-Service datastructure may be configured or designed for tracking system loadcharacteristics and conditions associated with different services whichare running within the storage system. In at least one embodiment, theLOAD-Service data structure 1000 may be used for tracking current orupdated LOAD conditions for selected service(s) running at the storagecluster. In one embodiment, the LOAD-Service data structure 1000 may beused for tracking current or updated LOAD conditions for each activeslice service running at the storage cluster.

An example embodiment of the LOAD-Service data structure 1000 will nowbe described by way of example with reference to the storage systemconfiguration illustrated in FIG. 9. As illustrated in the exampleembodiment of FIG. 10, the LOAD-Service data structure 1000 may includea plurality of records (or entries) (e.g., 1001, 1003, 1005) relating tospecifically identified services within the storage cluster (e.g., 910,FIG. 9). In at least one embodiment, each record may include one or moreof the following types of information (or combinations thereof):

-   -   Service Identifier information (e.g., Service_ID 1002) which        identifies a specific Service running at the storage cluster;    -   System Load information (e.g., LOAD(Service) 1004) which may        include a value (e.g., LOAD(Service) value) representing the        real-time (or near real-time) degree or amount of system load or        stress associated the identified Service.

According to different embodiments, the LOAD(Service) value for a givenService may be automatically and/or dynamically calculated by thestorage system (e.g., in real-time) based, at least partially, onmeasured amount(s) of read latency and/or write latency relating to readand/or write operations associated with the identified Service. Forexample, in one embodiment, the system may utilize the LOAD(Service)Analysis Procedure 1300 (FIG. 13A) to populate and/or update theLOAD-Service data structure 1000.

FIG. 11 illustrates an alternate example embodiment of a LOAD-Servicedata structure 1100 which may be configured or designed for trackingsystem load characteristics and conditions associated with differentservices which are running within the storage system. As illustrated inthe example embodiment of FIG. 11, the LOAD-Service data structure 1100may include a plurality of records (or entries) (e.g., 1101, 1103, 1105)relating to specifically identified services within the storage cluster.In at least one embodiment, each record may include one or more of thefollowing types of information (or combinations thereof):

-   -   Service Identifier information (e.g., Service_ID 1102) which        identifies a specific Service running at the storage cluster;    -   LOAD(Read) information 1104 which may include a LOAD(Read value        representing the real-time (or near real-time) degree or amount        of read-related system load or stress associated with the        identified Service;    -   LOAD(Write) information 1104 which may include a LOAD(Write)        value representing the real-time (or near real-time) degree or        amount of write-related system load or stress associated with        the identified Service.

According to different embodiments, the LOAD(Read) values may beautomatically and/or dynamically calculated (e.g., in real-time) based,at least partially, on measured amount(s) of read I/O latency which areassociated with the identified Service. According to differentembodiments, the LOAD(Write) values may be automatically and/ordynamically calculated (e.g., in real-time) based, at least partially,on measured amount(s) of write I/O latency and/or write cache queuedepth(s) which are associated with the identified Service.

FIG. 12 illustrates a specific example embodiment of a Client-Servicedata structure 1200. In at least one embodiment, the Client-Service datastructure 1200 may be configured or designed for tracking the respectiveServices which have been assigned to handle read/write operationsassociated with each Client interacting with the storage cluster. Forillustrative purposes, the example Client-Service data structureembodiment of FIG. 12 will now be described by way of example withreference to the storage system configuration illustrated in FIG. 9. Asillustrated in the example embodiment of FIG. 12, the Client-Servicedata structure 1200 may include a plurality of records (or entries)(e.g., 1201, 1203, 1205) each relating to a specifically identifiedClient of the storage system. In at least one embodiment, each recordmay include one or more of the following types of information (orcombinations thereof):

-   -   Client Identifier information (e.g., Client_ID 1202) which        identifies a specific Client (e.g., Client A, Client B, Client        C, etc.). In some embodiments, each Client which interacts with        the storage cluster may have associated therewith a respectively        unique connection identifier (Connection_ID which may be used by        the system to identify and track communications, requests (e.g.,        read/write requests), activities, and/or other information which        is associated with a given Client. Thus, for example, in one        embodiment, the Client_ID portion 1202 of a given Client-Service        data record (e.g., 1201) may be represented using that Client's        assigned Connection_ID identifier.    -   Primary slice service_ID information 1204 which identifies the        primary slice service assigned to handle communications with the        identified Client, including the servicing of read/write        requests originating from the identify client.    -   Associated Replication Service_ID(s) information 1206 which        identifies one or more secondary Service(s) associated with the        identified client, such as, for example, those Services which        have been assigned to handle metadata (e.g., slice) and/or data        replication tasks which are associated with the identified        Client.

In at least one embodiment, each node in the Cluster reports to eachother node its calculated load values. In this way each node (and/orService) may be informed about each other node's (and/or Service's) loadvalues. This information may be used to determine (e.g., on the sliceservice to which the Client is connected), the load value of the nodesand/or Services in the cluster of which that Client is using.

Load values can be calculated or determined using the sharednode/Service resource usage information. In some embodiments, thestorage system may be configured or designed to distinguish betweenoverloaded conditions which are due to or caused by different Systemload values such as, for example, one or more of the following (orcombinations thereof): reads, writes, bandwidth, compression, etc. Forexample, in at least one embodiment, the storage system may determinethat the system (or portion thereof) is: read overloaded, writeoverloaded, bandwidth overloaded, compression overloaded, etc.

In at least one embodiment, the calculated load values(which, forexample, may be unique to at least one Client volume) may be used by,along with client metrics, the target performance manager 402 (of FIG.4) to determine a target performance value to be implemented for eachrespective Client.

Example Procedures And Flow Diagrams

FIGS. 13-17 illustrate various example embodiments of differentprocedures and/or procedural flows which may be used for facilitatingactivities relating to one or more of the storage system QoS aspectsdisclosed herein.

FIG. 13A shows a flow diagram of a LOAD(Service) Analysis Procedure 1300in accordance with a specific embodiment. Additional, fewer, ordifferent operations of the procedure 1300 may be performed, dependingon the particular embodiment. The procedure 1300 can be implemented on acomputing device. In one implementation, the procedure 1300 is encodedon a computer-readable medium that contains instructions that, whenexecuted by a computing device, cause the computing device to performoperations of the procedure 1300. According to different embodiments, atleast a portion of the various types of functions, operations, actions,and/or other features provided by the LOAD(Service) Analysis Proceduremay be implemented at one or more nodes and/or volumes of the storagesystem. In at least one embodiment, the LOAD(Service) Analysis Proceduremay be operable to perform and/or implement various types of functions,operations, actions, and/or other features relating to the analysis,measurement, calculation, and updating of LOAD information for one ormore selected Services running at the storage cluster. According tospecific embodiments, multiple instances or threads of the LOAD(Service)Analysis Procedure may be concurrently implemented and/or initiated viathe use of one or more processors and/or other combinations of hardwareand/or hardware and software.

According to different embodiments, one or more different threads orinstances of the LOAD(Service) Analysis Procedure may be automaticallyand/or dynamically initiated and/or implemented at one or more differenttime intervals (e.g., during a specific time interval, at regularperiodic intervals, at irregular periodic intervals, upon demand, etc.).

As illustrated in the example embodiment of FIG. 13A, at 1302 it isassumed that at least one condition or event has been detected forinitiating execution of the LOAD(Service) Analysis Procedure. Forexample, in one embodiment, a given instance of the LOAD(Service)Analysis Procedure may be configured or designed to automatically run ona schedule, e.g., every 500 ms, 1 s, 10 s, 20 s, etc., to therebyanalyze and determine an updated LOAD(Service) value for the identifiedService. In some embodiments, the frequency of execution of theLOAD(Service) Analysis Procedure for a given Service may automaticallyand/or dynamically vary based on other events and/or conditions such as,for example, system metrics, client metrics, changes in QoS managementpolicies, etc.

As shown at 1304, the LOAD(Service) Analysis Procedure may initiateanalysis of system and/or client metrics for the identified Service. Inat least one embodiment, the analysis of system and/or client metricsmay include measuring, acquiring, and/or determining real-timeinformation relating to read latency and/or write latency for readand/or write operations associated with the identified Service.

As shown at 1306, the LOAD(Service) Analysis Procedure may determine acurrent LOAD(Service) value for the identified Service. According todifferent embodiments, the LOAD(Service) value may be determined orcalculated, for example, using one or more of the various LOADcalculation techniques described herein.

As shown at 1308, an optional determination can be made as to whether ornot the current calculated LOAD(Service) value for the selected Servicehas changed from a previously calculated LOAD(Service) value. Forexample, in one embodiment, the LOAD(Service) Analysis Procedure may usethe Service_ID of the identified Service to retrieve or access theLOAD(Service) value (e.g., 904, FIG. 9) from the local LOAD-ServiceTable (e.g., 900, FIG. 9), which, for example, may represent the mostrecent historical LOAD value for the identified Service. In at least oneembodiment, the LOAD(Service) Analysis Procedure may compare thecurrently calculated LOAD(Service) value to the correspondingLOAD(Service) value retrieved from the LOAD-Service Table in order todetermine whether or not the current calculated LOAD(Service) value forthe selected Service has changed.

In one embodiment, if it is determined that the current calculatedLOAD(Service) value for the selected Service has not changed from theLOAD(Service) value stored in the LOAD-Service Table, no additionalactions may be needed at this time. Alternatively, if it is determinedthat the current calculated LOAD(Service) value for the selected Servicehas changed from the SLOAD(Service) value stored in the LOAD-ServiceTable calculated LOAD(Service) value, the currently calculatedLOAD(Service) value for the selected Service may be stored (1310) in thelocal LOAD-Service Table. Additionally, information and/or notificationrelating to this update of the LOAD(Service) value for the selectedService may be pushed (1312) to one or more of the other nodes of thestorage cluster. In at least one embodiment, upon receiving theLOAD(Service) value notification update, the other node(s) mayautomatically and dynamically update their respective local LOAD-ServiceTables using the updated LOAD(Service) value information.

FIG. 13B shows a flow diagram of a LOAD(Read) Analysis Procedure 1330 inaccordance with a specific embodiment. Additional, fewer, or differentoperations of the procedure 1330 may be performed, depending on theparticular embodiment. The procedure 1330 can be implemented on acomputing device. In one implementation, the procedure 1330 is encodedon a computer-readable medium that contains instructions that, whenexecuted by a computing device, cause the computing device to performoperations of the procedure 1330. According to different embodiments, atleast a portion of the various types of functions, operations, actions,and/or other features provided by the LOAD(Read) Analysis Procedure maybe implemented at one or more nodes and/or volumes of the storagesystem. In at least one embodiment, the LOAD(Read) Analysis Proceduremay be operable to perform and/or implement various types of functions,operations, actions, and/or other features relating to the analysis,measurement, calculation, and updating of LOAD information forread-related transactions associated with one or more selected Servicesrunning at the storage cluster.

As illustrated in the example embodiment of FIG. 13B, at 1332 it isassumed that at least one condition or event has been detected forinitiating execution of the LOAD(Read) Analysis Procedure. As shown at1334, the LOAD(Read) Analysis Procedure may initiate analysis ofread-related system and/or client metrics for the identified Service. Inat least one embodiment, the analysis of system and/or client metricsmay include measuring, acquiring, and/or determining real-timeinformation relating to read latency for read operations handle by (orassociated with) the identified Service.

As shown at 1336, the LOAD(Read) Analysis Procedure may determine acurrent LOAD(Read) value for the identified Service. According todifferent embodiments, the LOAD(Read) value may be determined orcalculated, for example, using one or more of the various LOADcalculation techniques described herein.

As shown at 1338, an optional determination can be made as to whether ornot the current calculated LOAD(Read) value for the selected Service haschanged from a previously calculated LOAD(Read) value. For example, inone embodiment, the LOAD(Read) Analysis Procedure may use the Service_IDof the identified Service to retrieve or access the LOAD(Read) value(e.g., 1104, FIG. 11) from the local LOAD-Service Table (e.g., 1100,FIG. 11), which, for example, may represent the most recent historicalLOAD(Read) value for the identified Service. In at least one embodiment,the LOAD(Read) Analysis Procedure may compare the currently calculatedLOAD(Read) value to the corresponding LOAD(Read) value retrieved fromthe LOAD-Service Table 1100 in order to determine whether or not thecurrent calculated LOAD(Read) value for the selected Service haschanged.

In one embodiment, if it is determined that the current calculatedLOAD(Read) value for the selected Service has not changed from theLOAD(Read) value stored in the LOAD-Service Table, no additional actionsmay be needed at this time. Alternatively, if it is determined that thecurrent calculated LOAD(Read) value for the selected Service has changedfrom the SLOAD(Read) value stored in the LOAD-Service Table calculatedLOAD(Read) value, the currently calculated LOAD(Read) value for theselected Service may be stored (1340) in the local LOAD-Service Table1100. Additionally, information and/or notification relating to thisupdate of the LOAD(Read) value for the selected Service may be pushed(1342) to one or more of the other nodes of the storage cluster. In atleast one embodiment, upon receiving the LOAD(Read) value notificationupdate, the other node(s) may automatically and dynamically update theirrespective local LOAD-Service Tables using the updated LOAD(Read) valueinformation.

FIG. 13C shows a flow diagram of a LOAD(Write) Analysis Procedure 1350in accordance with a specific embodiment. Additional, fewer, ordifferent operations of the procedure 1350 may be performed, dependingon the particular embodiment. The procedure 1350 can be implemented on acomputing device. In one implementation, the procedure 1350 is encodedon a computer-readable medium that contains instructions that, whenexecuted by a computing device, cause the computing device to performoperations of the procedure 1350. According to different embodiments, atleast a portion of the various types of functions, operations, actions,and/or other features provided by the LOAD(Write) Analysis Procedure maybe implemented at one or more nodes and/or volumes of the storagesystem. In at least one embodiment, the LOAD(Write) Analysis Proceduremay be operable to perform and/or implement various types of functions,operations, actions, and/or other features relating to the analysis,measurement, calculation, and updating of LOAD information forwrite-related transactions associated with one or more selected Servicesrunning at the storage cluster.

As illustrated in the example embodiment of FIG. 13C, at 1352 it isassumed that at least one condition or event has been detected forinitiating execution of the LOAD(Write) Analysis Procedure. As shown at1354, the LOAD(Write) Analysis Procedure may initiate analysis ofwrite-related system and/or client metrics for the identified Service.In at least one embodiment, the analysis of system and/or client metricsmay include measuring, acquiring, and/or determining real-timeinformation relating to write latency for write operations handle by (orassociated with) the identified Service.

As shown at 1356, the LOAD(Write) Analysis Procedure may determine acurrent LOAD(Write) value for the identified Service. According todifferent embodiments, the LOAD(Write) value may be determined orcalculated, for example, using one or more of the various LOADcalculation techniques described herein.

As shown at 1358, an optional determination can be made as to whether ornot the current calculated LOAD(Write) value for the selected Servicehas changed from a previously calculated LOAD(Write) value. For example,in one embodiment, the LOAD(Write) Analysis Procedure may use theService_ID of the identified Service to retrieve or access theLOAD(Write) value (e.g., 1106, FIG. 11) from the local LOAD-ServiceTable (e.g., 1100, FIG. 11), which, for example, may represent the mostrecent historical LOAD(Write) value for the identified Service. In atleast one embodiment, the LOAD(Write) Analysis Procedure may compare thecurrently calculated LOAD(Write) value to the corresponding LOAD(Write)value retrieved from the LOAD-Service Table 1100 in order to determinewhether or not the current calculated LOAD(Write) value for the selectedService has changed.

In one embodiment, if it is determined that the current calculatedLOAD(Write) value for the selected Service has not changed from theLOAD(Write) value stored in the LOAD-Service Table, no additionalactions may be needed at this time. Alternatively, if it is determinedthat the current calculated LOAD(Write) value for the selected Servicehas changed from the SLOAD(Write) value stored in the LOAD-Service Tablecalculated LOAD(Write) value, the currently calculated LOAD(Write) valuefor the selected Service may be stored (1360) in the local LOAD-ServiceTable 1000. Additionally, information and/or notification relating tothis update of the LOAD(Write) value for the selected Service may bepushed (1362) to one or more of the other nodes of the storage cluster.In at least one embodiment, upon receiving the LOAD(Write) valuenotification update, the other node(s) may automatically and dynamicallyupdate their respective local LOAD-Service Tables using the updatedLOAD(Write) value information.

FIG. 14 shows a flow diagram of a LOAD(Client) Analysis Procedure 1400in accordance with a specific embodiment. Additional, fewer, ordifferent operations of the procedure 1400 may be performed, dependingon the particular embodiment. The procedure 1400 can be implemented on acomputing device. In one implementation, the procedure 1400 is encodedon a computer-readable medium that contains instructions that, whenexecuted by a computing device, cause the computing device to performoperations of the procedure 1400. According to different embodiments, atleast a portion of the various types of functions, operations, actions,and/or other features provided by the LOAD(Client) Analysis Proceduremay be implemented at one or more nodes and/or volumes of the storagesystem. For example, in one embodiment, the LOAD(Client) AnalysisProcedure may be initiated and/or performed by the primary slice servicewhich has been assigned for handling read/write communications with theidentified Client. In at least one embodiment, the LOAD(Client) AnalysisProcedure may be operable to perform and/or implement various types offunctions, operations, actions, and/or other features relating to theanalysis, measurement, calculation, and updating of LOAD information forone or more selected Clients of the storage system.

According to specific embodiments, multiple instances or threads of theLOAD(Client) Analysis Procedure may be concurrently implemented and/orinitiated via the use of one or more processors and/or othercombinations of hardware and/or hardware and software. In oneembodiment, a separate instance or thread of the LOAD(Client) AnalysisProcedure may be initiated for each respective Client of the storagesystem. In the specific example embodiment of FIG. 14, it is assumedthat the LOAD(Client) Analysis Procedure has been instantiated todynamically determine a current or updated LOAD(Client) value for aselected Client (e.g., Client A, FIG. 9).

According to different embodiments, one or more different threads orinstances of the LOAD(Client) Analysis Procedure may be automaticallyand/or dynamically initiated and/or implemented at one or more differenttime intervals (e.g., during a specific time interval, at regularperiodic intervals, at irregular periodic intervals, upon demand, etc.).For example, in one embodiment, a given instance of the LOAD(Client)Analysis Procedure may be configured or designed to automatically runabout every 10-20 sec (e.g., for a given Client) to thereby analyze anddetermine an updated LOAD(Client) value for the identified Client. Insome embodiments, the frequency of execution of the LOAD(Client)Analysis Procedure for a given Client may automatically and/ordynamically vary based on other events and/or conditions such as, forexample, system metrics, client metrics, changes in QoS managementpolicies, etc.

In the example embodiment of FIG. 14, at 1402 it is assumed that atleast one condition or event has been detected for initiating executionof the LOAD(Client) Analysis Procedure. As shown at 1404, theLOAD(Client) Analysis Procedure may initiate analysis of system and/orclient metrics. In at least one embodiment, the analysis of systemand/or client metrics may include measuring, acquiring, and/ordetermining real-time information relating to read latency and/or writelatency for read/write operations associated with the identified Client.

In the specific example embodiment of FIG. 14, the process ofdetermining a current LOAD(Client) value for the identified Client(e.g., Client A) may include identifying (1406) the appropriateService(s) which are associated with selected Client, and which are tobe factored into the computation of the LOAD(Client) value. In thisexample, it is assumed that the LOAD(Client) value is a client-specificvalue which reflects real-time system load for selected Services (e.g.,primary slice service, replication services) which have been identifiedas being associated with the identified Client. For example, in oneembodiment, the LOAD(Client) Analysis Procedure may use the Client_ID ofthe identified Client to access information from the localClient-Service data structure (e.g., 1100, FIG. 11) in order to identifythe specific Services which are associated with the identified Client(e.g., for purposes of LOAD(Client) calculation). By way of example,referring to the specific example embodiment of the Service-Client datastructure 1100 of FIG. 11, if it is assumed that the identified Clientcorresponds to Client A, the specific Services associated with Client Amay be identified as Service A (e.g., which has been assigned as theprimary slice service of Client A), and Service C (e.g., which has beenassigned as a secondary Service of Client A for handling replication ofClient A data/metadata).

As shown at 1408, a current LOAD(Client) value for the identified Clientmay be dynamically determined or calculated. According to differentembodiments, the LOAD(Client) value may be dynamically determined orcalculated, for example, using one or more of the various LOAD(Client)calculation techniques described herein. For example, in one embodiment,a current LOAD(Client) value for Client A may be dynamically calculatedaccording to:

LOAD(Client A)=MAX_VALUE {(LOAD(Read@Service A), LOAD(Write@(Service A)LOAD(Write@Service C)}.

In at least one embodiment, the calculated LOAD(Client) value may berepresentative of relative degree or amount of system resource load orstress relating to IO activities associated with the Service(s) (e.g.,primary Service and secondary Service(s)) which have been assigned tohandle read, write and replication operations for the identified Client.In at least one embodiment, the storage system may be configured ordesigned to differentiate between read and write related transactions,and to separately analyze, determine and/or track LOAD(Read) andLOAD(Write) values associated with the identified Client. Exampleembodiments of such techniques are illustrated, for example, in FIGS.16, 17, 20, and 21, and described in greater detail below.

One concern with the QoS implementation in the storage system is thatclients of relatively “lower” importance may cause or contribute toincreased latencies in the storage cluster, making it more difficult forthose Clients of relatively higher importance (e.g., with relativelyhigher minimum QoS performance guarantees) to get fair, proportionalthroughput of the system.

By way of example with reference to FIG. 9, it may be assumed that thestorage cluster 910 has been configured to implement the following QoSperformance guarantees:

Client A (902) volume set at 15 k MIN IOPS

40 other Client volumes (including Clients B and C) set at 1 k MIN IOPS

IOs for each Client are 80% read IOPS and 20% write IOPS

Size of each IO transaction is 4 kb.

In this example embodiment, it may be assumed for illustrative purposesthat the storage system is not able to provide Client A with thespecified minimum guaranteed 15 k IOPS. Further, in this example, it isassumed that any increased read latency is caused by the other 40 Clientvolumes driving heavy read workloads. In at least one embodiment, thestorage system may be configured or designed to dynamically determinethat, because the Client A workload is read IOPS heavy, the write-basedLOAD values may not play a significant role in the detected increase inread latency which may be contributing to the inability of Client A toachieve its MIN IOPS guarantees.

Target Performance Value Calculations

As noted above, the target performance manager 402 calculates a targetperformance value based upon system load values, client load values, andclient QoS parameters. The target performance value is then used tocontrol how the client can access resources of the storage system

FIG. 15 shows a flow diagram of a QoS Client Policy Management Procedure1500 in accordance with a specific embodiment. Additional, fewer, ordifferent operations of the procedure 1500 may be performed, dependingon the particular embodiment. The procedure 1500 can be implemented on acomputing device. In one implementation, the procedure 1500 is encodedon a computer-readable medium that contains instructions that, whenexecuted by a computing device, cause the computing device to performoperations of the procedure 1500. According to different embodiments, atleast a portion of the various types of functions, operations, actions,and/or other features provided by the QoS Client Policy ManagementProcedure may be implemented at one or more nodes and/or volumes of thestorage system. For purposes of illustration, it is assumed that the QoSClient Policy Management Procedure 1500 has been instantiated to performQoS policy management for a selected Client (e.g., Client A, FIG. 9).

In at least one embodiment, the QoS Client Policy Management Proceduremay be operable to perform and/or implement various types of functions,operations, actions, and/or other features relating to the analysis,measurement, calculation, and updating of LOAD information for one ormore selected Clients of the storage system. According to specificembodiments, multiple instances or threads of the QoS Client PolicyManagement Procedure may be concurrently implemented and/or initiatedvia the use of one or more processors and/or other combinations ofhardware and/or hardware and software. In one embodiment, a separateinstance or thread of the QoS Client Policy Management Procedure may beinitiated for performing or facilitating QoS policy management for eachrespective Client of the storage system.

According to different embodiments, one or more different threads orinstances of the QoS Client Policy Management Procedure may beautomatically and/or dynamically initiated and/or implemented at one ormore different time intervals (e.g., during a specific time interval, atregular periodic intervals, at irregular periodic intervals, upondemand, etc.). For example, in one embodiment, a given instance of theQoS Client Policy Management Procedure may be configured or designed toautomatically run about every 250-1000 milliseconds (e.g., every 500 msfor a given Client) to thereby analyze and determine an updatedLOAD(Client) value for the identified Client. In some embodiments, thefrequency of execution of the QoS Client Policy Management Procedure fora given Client may automatically and/or dynamically vary based on otherevents and/or conditions such as, for example, system metrics, clientmetrics, changes in QoS management policies, etc.

In the example embodiment of FIG. 15, at 1502 it is assumed that atleast one condition or event has been detected for initiating executionof the QoS Client Policy Management Procedure. As shown at 1504, the QoSClient Policy Management Procedure may initiate analysis of systemand/or client metrics. In at least one embodiment, the analysis ofsystem and/or client metrics may include measuring, acquiring, and/ordetermining real-time information relating to read latencies and/orwrite latencies for IO activities associated with the Service(s) (e.g.,primary Service and secondary Service(s)) which have been assigned tohandle read, write and replication operations for the identified Client.

As shown at 1506, the QoS Client Policy Management Procedure maydetermine a current Load(Client) value for the identified Client.According to different embodiments, the Load(Client) value may bedetermined or calculated, for example, using one or more of the variousLoad(Client) calculation techniques described herein. In the specificexample embodiment of FIG. 15, it is assumed that the Load(Client) valueis a client-specific Load value which factors in both read latency andwrite latency metrics for IO activities associated with the Service(s)(e.g., primary Service and secondary Service(s)) which have beenassigned to handle read, write and replication operations for theidentified Client.

As shown at 1508, the QoS Client Policy Management Procedure may analyzethe current Load(Client) value, and in response, may select andimplement an appropriate QoS Management Policy for the identifiedClient. For example, as illustrated in the example embodiment of FIG.15:

-   -   If it is determined that Load(Client)<Threshold Value A1, the        QoS Client Policy Management Procedure may implement (1510) QoS        Management Policy Set A1;    -   If it is determined that Threshold Value        A1≧Load(Client)≧Threshold Value A2, the QoS Client Policy        Management Procedure may implement (1512) QoS Management Policy        Set B1;    -   If it is determined that Load(Client)>Threshold Value A2, the        QoS Client Policy Management Procedure may implement (1514) QoS        Management Policy Set C1.

In at least one embodiment, the storage system may be configured ordesigned to: (1) differentiate between read and write relatedtransactions, and to separately analyze, determine and/or trackLoad(Client-Read) and Load(Client-Write) values associated with a givenClient; and (2) independently evaluate and implement differentrespective QoS Management Policy sets for Client-related Read IOPS andClient-related Write IOPS. Example embodiments of such techniques areillustrated, for example, in FIGS. 16, 17, 20, and 21, and described ingreater detail below.

FIG. 18 shows a graphical representation illustrating how the storagesystem may implement aspects of a QoS Client Policy Management Proceduresuch as that described with reference to FIG. 15. As illustrated in theexample embodiment of FIG. 18, an X-Y graph portion 1800 is shown whichincludes a Y-axis representing target performance values correspondingto client IOPS 1810 (e.g., both read and write IOPS) and an X-axisrepresenting a selected Load value (Load A, 1801). For purposes ofillustration, it is assumed Load A corresponds to the Load(Client)metric for a selected Client (e.g., Client A). However, it will beappreciated that, in alternate embodiments (not shown) Load A maycorrespond to one of a variety of different metrics described hereinsuch as, for example, one or more of the following (or combinationsthereof): Load(Service); Load(Read); Load(Write); Load(Write_Buffer);Load(Client-Read); Load(Client-Write); etc.

As illustrated in the example embodiment of FIG. 18, graph portion 1800includes reference lines 1803, 1805, 1807 which represent the min IOPSQoS parameter 1805; max IOPS QoS parameter 1805; and max burst IOPS QoSparameter 1807 for the identified Client. Additionally, graph portion1800 includes reference lines 1811, 1813, 1815 which, in this exampleembodiment, represent threshold values which may be used to determineand select the current QoS Management Policy Set in effect for theidentified Client. For example, as illustrated in FIG. 18:

-   -   During times when Load A<Threshold Value A1, QoS Management        Policy Set A1 may be set into effect for the identified Client.        In the specific example embodiment of FIG. 18, region 1802        provides a graphical representation of the possible values of        IOPS that a client can operate at in accordance with the QoS        Management Policy Set A1. In this example embodiment, the QoS        Management Policy Set A1 may specify that the Client is allowed        to accrue IOPS credits, and that the Client's IOPS: can be equal        to or less than the Client's max IOPS QoS parameter 1805; may be        allowed to operate above the Client's max burst IOPS QoS        parameter based upon accrued credits; but is not to exceed the        Client's max burst IOPS QoS parameter 1807.    -   During times when Threshold Value A1≧Load A≧Threshold Value A2,        QoS Management Policy Set B1 may be set into effect for the        identified Client. In the specific example embodiment of FIG.        18, region 1804 provides a graphical representation of the range        of IOPS that a client can perform. In this example embodiment,        the QoS Management Policy Set B1 may specify that the Client's        IOPS are to be throttled to a target performance IOPS value        which is within a range between the Client's max IOPS QoS        parameter and min IOPS QoS parameter. A client can of course use        less IOPS that the minimum IOPS depending upon client's use of        the storage system. Additionally, the QoS Management Policy Set        B1 may also specify that: (i) that the Client's IOPS are not to        exceed the Client's max IOPS QoS parameter; and (ii) the        throttling of the Client's IOPS increases as the Client's        Load(Client) value increases from Threshold Value A1 (1811) to        Threshold Value A2 (1813).    -   During times when Load A>Threshold Value A2, QoS Management        Policy Set C1 may be set into effect for the identified Client.        In the specific example embodiment of FIG. 18, region 1806        provides a graphical representation of the possible values of        IOPS that a client can operate at in accordance with the QoS        Management Policy Set C1. In this example embodiment, the QoS        Management Policy Set B1 may specify that the Client's IOPS are        to be throttled to a target performance IOPS value which is        within a range between the Client's min IOPS QoS parameter and        zero. Additionally, the QoS Management Policy Set C1 may also        specify that the throttling of the Client's IOPS increases as        the Client's Load(Client) value increases from Threshold Value        A2 (1813) to Threshold Value A3 (1815).

FIG. 19A shows a graphical representation illustrating an exampleembodiment of how different QoS Management Policy Sets for throttlingClient IOPS may be automatically and/or dynamically implemented inresponse changing Load(Client) conditions. As illustrated in the exampleembodiment of FIG. 19A, an X-Y graph portion 1900 is shown whichincludes a Y-axis representing target performance values correspondingto Client IOPS 1910 (e.g., both read and write IOPS) and an X-axisrepresenting a client Load(Client) metric for a selected Client (e.g.,Client A). As illustrated in the example embodiment of FIG. 19A, graphportion 1900 includes reference lines 1903, 1905, 1907 which representthe min IOPS QoS parameter 1905; max IOPS QoS parameter 1905; and maxburst IOPS QoS parameter 1907 for the identified Client. Additionally,graph portion 1900 includes reference lines 1911, 1913, 1915 which, inthis example embodiment, represent threshold values which may be used todetermine and select the current QoS Management Policy Set to be putinto effect for the identified Client. For example, as illustrated inFIG. 19A:

-   -   During times when Load(Client)<Threshold Value A1, QoS        Management Policy Set A1 may be set into effect for the        identified Client. In the specific example embodiment of FIG.        19A, region 1902 provides a graphical representation of the        possible values of IOPS that a client can operate at in        accordance with the QoS Management Policy Set A1. In this        example embodiment, the QoS Management Policy Set A1 may specify        that the Client is allowed to accrue IOPS credits, and that the        Client's IOPS: can be equal to or less than the Client's max        IOPS QoS parameter 1905; may be allowed to operate above the        Client's max burst IOPS QoS parameter based upon accrued        credits; but is not to exceed the Client's max burst IOPS QoS        parameter 1907. In one embodiment, the Threshold Value A1 may be        defined to be a numeric value within the range of 0.2-0.4 (e.g.,        Threshold Value A1=0.33);    -   During times when Threshold Value A1≧Load(Client)≧Threshold        Value A2, QoS Management Policy Set B1 may be set into effect        for the identified Client. In the specific example embodiment of        FIG. 19A, region 1904 provides a graphical representation of the        possible values of IOPS that a client can operate at in        accordance with the QoS Management Policy Set B1. In this        example embodiment, the QoS Management Policy Set B1 may specify        that the Client's IOPS are to be throttled to a target        performance IOPS value which is within a range between the        Client's max IOPS parameter and min IOPS parameter.        Additionally, the QoS Management Policy Set B1 may also specify        that, at any given time (while Threshold Value        A1≧Load(Client)≧Threshold Value A2), the Client's IOPS are to be        throttled to a target performance IOPS value which is        dynamically determined based on the Client's current (e.g.,        real-time) Load(Client) value. For example, in the example        embodiment of FIG. 19A, while the QoS Management Policy Set B1        is in effect, the Client's IOPS are to be throttled to a target        performance IOPS value which does not exceed the corresponding        IOPS value defined by boundary curve 1904 a (e.g., which defines        the upper limit of the Client's allowable IOPS relative to the        Client's current Load(Client) value). In one embodiment, the        Threshold Value A2 may be defined to be a numeric value within        the range of 0.5-0.8 (e.g., Threshold Value A2=0.66);    -   During times when Load(Client)>Threshold Value A2, QoS        Management Policy Set C1 may be set into effect for the        identified Client. In the specific example embodiment of FIG.        19A, region 1906 provides a graphical representation of the        possible values of IOPS that a client can operate at in        accordance with the QoS Management Policy Set C1. In this        example embodiment, the QoS Management Policy Set C1 may specify        that the Client's IOPS are to be throttled to a target        performance IOPS value which is within a range between the        Client's min IOPS parameter and zero. Additionally, the QoS        Management Policy Set C1 may also specify that, at any given        time (Load(Client)>Threshold Value A2), the Client's IOPS are to        be throttled to an target performance IOPS value which is        dynamically determined based on the Client's Load(Client) value.        For example, in the example embodiment of FIG. 19A, while the        QoS Management Policy Set C1 is in effect, the Client's IOPS are        to be throttled to an IOPS value which does not exceed the        corresponding IOPS value defined by boundary curve 1906 a (e.g.,        which defines the upper limit of the Client's allowable IOPS        relative to the Client's current Load(Client) value). In one        embodiment, the Threshold Value A3 may be defined to be a        numeric value within the range of 0.75-1.0 (e.g., Threshold        Value A3=0.85)

According to different embodiments, QoS Management Policy Sets (and IOPSboundary curves associated therewith) may be Client specific, and maytherefore differ for one or more Clients. For example, in one embodimentthe QoS Management Policy Sets which may be implemented for Client A maydiffer from the QoS Management Policy Sets implemented for Clients B andC. Additionally, in at least one embodiment, IOPS throttling may beindependently implemented and managed across multiple different Clientson a per Client basis.

For example, FIG. 19B shows an example embodiment illustrating how QoSManagement and IOPS throttling may be simultaneously, independently, anddynamically implemented for multiple different Clients (e.g., Client A,Client B, Client C) of the storage system. As illustrated in the exampleembodiment of FIG. 19B, an X-Y graph portion 1950 is shown whichincludes a Y-axis representing target performance values correspondingto client IOPS 1910 (e.g., both read and write IOPS) and an X-axisrepresenting client Load(Client) values.

As illustrated in the example embodiment of FIG. 19B, graph portion 1950includes indications of the each Client's min IOPS QoS parameter 1903,max IOPS QoS parameter 1905; and max burst IOPS QoS parameter 1909.Additionally, graph portion 1950 includes reference lines 1911, 1913,1915 which, in this example embodiment, represent threshold values whichmay be used to determine the particular QoS Management Policy Set(s) tobe used for determining QoS management and/or IOPS throttling for eachClient.

In the specific example embodiment of FIG. 19B, it is assumed, for easeof illustration, that the min IOPS, max IOPS, and max burst IOPS valuesfor Clients A, B, C are identical. However, in other embodiments, therespective the min IOPS, max IOPS, and max burst IOPS values for ClientsA, B, C may differ for each Client. Similarly, it is assumed for ease ofillustration, that the same LOAD threshold values (e.g., A1, A2, A3) areto be applied to Clients A, B, C. However, in other embodiments, eachClient may have associated therewith a respective set of LOAD thresholdvalues which may be used for determining the particular QoS ManagementPolicy Set(s) to be used for that Client.

As illustrated in the example embodiment of FIG. 19B, it is assumed, forpurposes of illustration, that Client A's current LOAD value(“LOAD(Client A)”) 1962 has been calculated to be LOAD(Client A)=0.23,which is assumed to be less than the LOAD(Client) Threshold Value A1.Accordingly, in this example embodiment, the Storage system maydetermine that QoS Management Policy Set A1 is to be used fordetermining the Target IOPS value for Client A.

Thus, for example, in the example embodiment of FIG. 19B, the TargetIOPS value for Client A may be determined by the coordinate (1962 a) atwhich the LOAD(Client A) value intersects with QoS Management Policy SetA1 (“QMPA1”) curve 1902 a. As illustrated in this example, the valuesassociated with coordinate 1962 a are: (0.23, 1.0, QMPA1), where:

-   -   0.23 represents the LOAD(Client A) value;    -   QMPA1 represents QoS Management Policy Set A1;    -   represents a scaled (and/or normalized) target IOPS ratio whose        value may be determined based on a function of the QoS        Management Policy Set A and the LOAD(Client) value. For example,        in the specific example embodiment of FIG. 19B, the target IOPS        ratio value may be determined by the point of intersection        (e.g., 1962 a) at which the LOAD(Client A) value intersects with        QoS Management Policy Set A1 (“QMPA1”) curve 1902 a.

In at least one embodiment, the Target IOPS value (e.g., T1) for ClientA may be expressed as a function which is relative to Client A's min andmax IOPS values, such as, for example:

TargetIOPS(ClientA)=T1

T2=(1.0*(MAX_(IOPS(ClientA))+MIN_(IOPS(ClientA))))+MIN_(IOPS(ClientA))

Thus, for example, the storage system may implement QoS Management forClient A's IOs by causing Client A's IOPS to be throttled (at leasttemporarily) to an IOPS value not to exceed T1. In the exampleembodiment of FIG. 19B, the Target IOPS value for Client A (T1) may bedetermined to be equal to Client A's MAX IOPS Value. Additionally, theQoS Management Policy Set A1 may also permit use of Client A's creditsfor enabling Client A's IOPS to burst above its respective MAX IOPSvalue.

Further, as illustrated in the example embodiment of FIG. 19B, it isassumed, for purposes of illustration, that Client B's current LOADvalue (“LOAD(Client B)”) 1972 has been calculated to be LOAD(ClientB)=0.39, which is assumed to be greater than the LOAD(Client) ThresholdValue A1, but less than LOAD(Client) Threshold Value A2. Accordingly, inthis example embodiment, the storage system may determine that QoSManagement Policy Set B1 is to be used for determining the Target IOPSvalue for Client B.

Thus, for example, in the example embodiment of FIG. 19B, the TargetIOPS value for Client B may be determined by the coordinate (1972 a) atwhich the LOAD(Client B) value intersects with QoS Management Policy SetB1 (“QMPB1”) curve 1904 a. As illustrated in this example, the valuesassociated with coordinate 1972 a are: (0.39, 0.48, QMPB1), where:

-   -   0.39 represents the LOAD(Client B) value;    -   QMPB1 represents QoS Management Policy Set B1;    -   0.48 represents a scaled (and/or normalized) target IOPS ratio        whose value may be determined based on a function of the QoS        Management Policy Set B and the LOAD(Client) value. For example,        in the specific example embodiment of FIG. 19B, the target IOPS        ratio value may be determined by the point of intersection        (e.g., 1972 a) at which the LOAD(Client B) value intersects with        QoS Management Policy Set B1 (“QMPB1”) curve 1904 a.

In at least one embodiment, the Target IOPS value (e.g., T2) for ClientB may be expressed as a function which is relative to Client B's MIN andMAX IOPS values, such as, for example:

TargetIOPS(ClientB)=T2

T2=(0.48*(MAX_(IOPS(ClientB))+MIN_(IOPS(ClientB))))+MIN_(IOPS(ClientB))

Thus, for example, the storage system may implement QoS Management forClient B's IOs by causing Client B's IOPS to be throttled (at leasttemporarily) to an IOPS value not to exceed T2.

Similarly, as illustrated in the example embodiment of FIG. 19B, it isassumed, for purposes of illustration, that Client C's current LOADvalue (“LOAD(Client C)”) 1982 has been calculated to be LOAD(ClientC)=0.55, which is assumed to be greater than the LOAD(Client) ThresholdValue A1, but less than LOAD(Client) Threshold Value A2. Accordingly, inthis example embodiment, the storage system may determine that QoSManagement Policy Set B1 is to be used for determining the Target IOPSvalue for Client C.

Thus, for example, in the example embodiment of FIG. 19B, the TargetIOPS value for Client C may be determined by the coordinate (1982 a) atwhich the LOAD(Client C) value intersects with QoS Management Policy SetB1 (“QMPB1”) curve 1904 a. As illustrated in this example, the valuesassociated with coordinate 1982 a are: (0.55, 0.18, QMPB1), where:

-   -   0.55 represents the LOAD(Client C) value;    -   QMPB1 represents QoS Management Policy Set B1;    -   0.19 represents a scaled (and/or normalized) target IOPS ratio        whose value may be determined based on a function of the QoS        Management Policy Set B and the LOAD(Client) value. For example,        in the specific example embodiment of FIG. 19B, the target IOPS        ratio value may be determined by the point of intersection        (e.g., 1982 a) at which the LOAD(Client C) value intersects with        QoS Management Policy Set B1 (“QMPB1”) curve 1904 a.

In at least one embodiment, the Target IOPS value (e.g., T3) for ClientC may be expressed as a function which is relative to Client C's MIN andMAX IOPS values, such as, for example:

TargetIOPS(ClientC)=T3

T3=(0.19*(MAX_(IOPS(ClientC))MIN_(IOPS(ClientC))))+MIN_(IOPS(ClientC))

Thus, for example, the Storage system may implement QoS Management forClient C's IOs by causing Client C's IOPS to be throttled (at leasttemporarily) to an IOPS value not to exceed T3.

Additionally, as illustrated in the example embodiment of FIG. 19B, itis assumed, for purposes of illustration, that Client D's current LOADvalue (“LOAD(Client D)”) 1992 has been calculated to be LOAD(ClientD)=0.74, which is assumed to be greater than the LOAD(Client) ThresholdValue A2. Accordingly, in this example embodiment, the Storage systemmay determine that QoS Management Policy Set C1 is to be used fordetermining the Target IOPS value for Client D.

Thus, for example, in the example embodiment of FIG. 19B, the TargetIOPS value for Client D may be determined by the coordinate (1992 a) atwhich the LOAD(Client D) value intersects with QoS Management Policy SetC1 (“QMPC1”) curve 1906 a. As illustrated in this example, the valuesassociated with coordinate 1992 a are: (0.74, 0.74, QMPC1), where:

-   -   0.74 represents the LOAD(Client D) value;    -   QMPC1 represents QoS Management Policy Set C1;    -   0.75 represents a scaled (and/or normalized) target IOPS ratio        whose value may be determined based on a function of the QoS        Management Policy Set C and the LOAD(Client) value. For example,        in the specific example embodiment of FIG. 19B, the target IOPS        ratio value may be determined by the point of intersection        (e.g., 1992 a) at which the LOAD(Client D) value intersects with        QoS Management Policy Set C1 (“QMPC1”) curve 1906 a.

In at least one embodiment, the Target IOPS value (e.g., T4) for ClientD may be expressed as a function which is relative to Client D's MIN andMAX IOPS values, such as, for example:

TargetIOPS(ClientD)=T4

T4=0.75*MIN_(IOPS(ClientD))

Thus, for example, the storage system may implement QoS Management forClient D's IOs by causing Client D's IOPS to be throttled (at leasttemporarily) to an IOPS value not to exceed T4.

It will be appreciated that, in at least some embodiments, the Storagesystem may proportionally throttle IOPS for each Client relative to thatClients defined range of MIN and MAX IOPS. In some embodiments, thedifferent QoS Management Policy Sets which are implemented for eachrespective client may have the effect of prioritizing some Clients overothers. Additionally, in some embodiments, the QoS Management PolicySets may preemptively decrease the target IOPS values for one or moreClients in order to help prevent the system from getting overloaded.

As mentioned previously, the storage system may be configured ordesigned to: (1) differentiate between read and write relatedtransactions, and to separately analyze, determine and/or trackLoad(Client-Read) and Load(Client-Write) values associated with a givenClient; and (2) independently evaluate and implement differentrespective QoS Management Policy sets for Client-related Read IOPS andClient-related Write IOPS. Example embodiments of such techniques areillustrated, for example, in FIGS. 16, 17, 20, and 21.

FIG. 16 shows a flow diagram of a QoS Client-Read Policy ManagementProcedure 1600 in accordance with a specific embodiment. Additional,fewer, or different operations of the procedure 1600 may be performed,depending on the particular embodiment. The procedure 1600 can beimplemented on a computing device. In one implementation, the procedure1600 is encoded on a computer-readable medium that contains instructionsthat, when executed by a computing device, cause the computing device toperform operations of the procedure 1600. According to differentembodiments, at least a portion of the various types of functions,operations, actions, and/or other features provided by the QoSClient-Read Policy Management Procedure may be implemented at one ormore nodes and/or volumes of the storage system. For purposes ofillustration, it is assumed that the QoS Client-Read Policy ManagementProcedure 1600 has been instantiated to perform QoS policy managementfor a selected Client (e.g., Client A, FIG. 9).

In at least one embodiment, the QoS Client-Read Policy ManagementProcedure may be operable to perform and/or implement various types offunctions, operations, actions, and/or other features relating to theanalysis, measurement, calculation, and updating of Load information forone or more selected Clients of the storage system. According tospecific embodiments, multiple instances or threads of the QoSClient-Read Policy Management Procedure may be concurrently implementedand/or initiated via the use of one or more processors and/or othercombinations of hardware and/or hardware and software. In oneembodiment, a separate instance or thread of the QoS Client-Read PolicyManagement Procedure may be initiated for performing or facilitating QoSpolicy management for each respective Client of the storage system.

According to different embodiments, one or more different threads orinstances of the QoS Client-Read Policy Management Procedure may beautomatically and/or dynamically initiated and/or implemented at one ormore different time intervals (e.g., during a specific time interval, atregular periodic intervals, at irregular periodic intervals, upondemand, etc.). For example, in one embodiment, a given instance of theQoS Client-Read Policy Management Procedure may be configured ordesigned to automatically run about every 250-1000 milliseconds (e.g.,every 500 ms for a given Client) to thereby analyze and determine anupdated Load(Client-Read) value for the identified Client. In someembodiments, the frequency of execution of the QoS Client-Read PolicyManagement Procedure for a given Client may automatically and/ordynamically vary based on other events and/or conditions such as, forexample, system metrics, client metrics, changes in QoS managementpolicies, etc.

In the example embodiment of FIG. 16, at 1602 it is assumed that atleast one condition or event has been detected for initiating executionof the QoS Client-Read Policy Management Procedure. As shown at 1604,the QoS Client-Read Policy Management Procedure may initiate analysis ofsystem and/or client metrics. In at least one embodiment, the analysisof system metrics may include measuring, acquiring, and/or determiningreal-time information relating to read latencies for IO activitiesassociated with the Service(s) which have been assigned to handle readoperations for the identified Client.

As shown at 1606, the QoS Client-Read Policy Management Procedure maydetermine a current Load(Client-Read) value for the identified Client.According to different embodiments, the Load(Client-Read) value may bedetermined or calculated, for example, using one or more of the variousLoad(Client-Read) calculation techniques described herein. In at leastone embodiment, the Load(Client-Read) value may be expressed as aclient-specific Load value which takes into account read latency metricsfor IO activities associated with the Service(s) which have beenassigned to handle read operations for the identified Client.

As shown at 1608, the QoS Client-Read Policy Management Procedure mayanalyze the current Load(Client-Read) value, and in response, may selectand implement an appropriate QoS Management Policy for the identifiedClient. For example, as illustrated in the example embodiment of FIG.16:

-   -   If it is determined that Load(Client-Read)<Threshold Value A1,        the QoS Client-Read Policy Management Procedure may implement        (1610) QoS Management Policy Set A2;    -   If it is determined that Threshold Value        A1≧Load(Client-Read)≧Threshold Value A2, the QoS Client-Read        Policy Management Procedure may implement (1612) QoS Management        Policy Set B2;    -   If it is determined that Load(Client-Read)>Threshold Value A2,        the QoS Client-Read Policy Management Procedure may implement        (1615) QoS Management Policy Set C2.

FIG. 20 shows a graphical representation illustrating an exampleembodiment of how different QoS Management Policy Sets for throttlingClient IOPS may be automatically and/or dynamically implemented inresponse changing Load(Client-Read) conditions. As illustrated in theexample embodiment of FIG. 20, an X-Y graph portion 2000 is shown whichincludes a Y-axis representing target performance values correspondingto Client read IOPS 2010 and an X-axis representing Load(Client-Read)values for a selected Client (e.g., Client A). As illustrated in theexample embodiment of FIG. 20, graph portion 2000 includes referencelines 2003, 2005, 2007 which represent the min read IOPS QoS parameter2003; max read IOPS QoS parameter 2005; and max burst read IOPS QoSparameter 2007 for the identified Client. Additionally, graph portion2000 includes reference lines 2011, 2013, 2015 which, in this exampleembodiment, represent threshold values which may be used to determineand select the current QoS Management Policy Set to be put into effectfor the identified Client. For example, as illustrated in FIG. 20:

-   -   During times when Load(Client-Read)<Threshold Value A2, QoS        Management Policy Set A2 may be set into effect for the        identified Client. In the specific example embodiment of FIG.        20, region 2002 provides a graphical representation of the        possible values of IOPS that a client can operate at in        accordance with the QoS Management Policy Set A2. In this        example embodiment, the QoS Management Policy Set A2 may specify        that the Client is allowed to accrue IOPS credits, and that the        Client's IOPS: can be equal to or less than the Client's max        IOPS QoS parameter 2005; may be allowed to operate above the        Client's max burst IOPS QoS parameter based upon accrued        credits; but is not to exceed the Client's max burst IOPS QoS        parameter 2007.    -   During times when Threshold Value A2≧Load(Client-Read)≧Threshold        Value A2, QoS Management Policy Set B2 may be set into effect        for the identified Client. In the specific example embodiment of        FIG. 20, region 2004 provides a graphical representation of the        possible values of IOPS that a client can operate at in        accordance with the QoS Management Policy Set B2. In this        example embodiment, the QoS Management Policy Set B2 may specify        that the Client's read IOPS are to be throttled to a target        performance IOPS value which is within a range between the        Client's max read IOPS QoS parameter and min read IOPS QoS        parameter. Additionally, the QoS Management Policy Set B2 may        also specify that, at any given time (while Threshold Value        A1≧Load(Client-Read)≧Threshold Value A2), the Client's read IOPS        are to be throttled to a target performance IOPS value which is        dynamically determined based on the Client's current (e.g.,        real-time) Load(Client-Read) value. For example, in the example        embodiment of FIG. 20, while the QoS Management Policy Set B2 is        in effect, the Client's read IOPS are to be throttled to a        target performance IOPS value which does not exceed the        corresponding IOPS value defined by boundary curve 2004 a (e.g.,        which defines the upper limit of the Client's allowable read        IOPS relative to the Client's current Load(Client-Read) value).    -   During times when Load(Client-Read)>Threshold Value A2, QoS        Management Policy Set C2 may be set into effect for the        identified Client. In the specific example embodiment of FIG.        20, region 2006 provides a graphical representation of the        possible values of IOPS that a client can operate at in        accordance with the QoS Management Policy Set C2. In this        example embodiment, the QoS Management Policy Set C2 may specify        that the Client's read IOPS are to be throttled to a target        performance IOPS value which is within a range between the        Client's min read IOPS QoS parameter and zero. Additionally, the        QoS Management Policy Set C2 may also specify that, at any given        time (Load(Client-Read)>Threshold Value A2), the Client's read        IOPS are to be throttled to a target performance IOPS value        which is dynamically determined based on the Client's        Load(Client-Read) value. For example, in the example embodiment        of FIG. 20, while the QoS Management Policy Set C2 is in effect,        the Client's read IOPS are to be throttled to an IOPS value        which does not exceed the corresponding IOPS value defined by        boundary curve 2006 a (e.g., which defines the upper limit of        the Client's allowable read IOPS relative to the Client's        current Load(Client-Read) value).

FIG. 17 shows a flow diagram of a QoS Client-Write Policy ManagementProcedure 1700 in accordance with a specific embodiment. Additional,fewer, or different operations of the procedure 1700 may be performed,depending on the particular embodiment. The procedure 1700 can beimplemented on a computing device. In one implementation, the procedure1700 is encoded on a computer-readable medium that contains instructionsthat, when executed by a computing device, cause the computing device toperform operations of the procedure 1700. According to differentembodiments, at least a portion of the various types of functions,operations, actions, and/or other features provided by the QoSClient-Write Policy Management Procedure may be implemented at one ormore nodes and/or volumes of the storage system. For purposes ofillustration, it is assumed that the QoS Client-Write Policy ManagementProcedure 1700 has been instantiated to perform QoS policy managementfor a selected Client (e.g., Client A, FIG. 9).

In at least one embodiment, the QoS Client-Write Policy ManagementProcedure may be operable to perform and/or implement various types offunctions, operations, actions, and/or other features relating to theanalysis, measurement, calculation, and updating of Load information forone or more selected Clients of the storage system. According tospecific embodiments, multiple instances or threads of the QoSClient-Write Policy Management Procedure may be concurrently implementedand/or initiated via the use of one or more processors and/or othercombinations of hardware and/or hardware and software. In oneembodiment, a separate instance or thread of the QoS Client-Write PolicyManagement Procedure may be initiated for performing or facilitating QoSpolicy management for each respective Client of the storage system.

According to different embodiments, one or more different threads orinstances of the QoS Client-Write Policy Management Procedure may beautomatically and/or dynamically initiated and/or implemented at one ormore different time intervals (e.g., during a specific time interval, atregular periodic intervals, at irregular periodic intervals, upondemand, etc.). For example, in one embodiment, a given instance of theQoS Client-Write Policy Management Procedure may be configured ordesigned to automatically run about every 250-1000 milliseconds (e.g.,every 500 ms for a given Client) to thereby analyze and determine anupdated Load(Client-Write) value for the identified Client. In someembodiments, the frequency of execution of the QoS Client-Write PolicyManagement Procedure for a given Client may automatically and/ordynamically vary based on other events and/or conditions such as, forexample, system metrics, client metrics, changes in QoS managementpolicies, etc.

In the example embodiment of FIG. 17, at 1702 it is assumed that atleast one condition or event has been detected for initiating executionof the QoS Client-Write Policy Management Procedure. As shown at 1704,the QoS Client-Write Policy Management Procedure may initiate analysisof system and/or client metrics. In at least one embodiment, theanalysis of system and/or client metrics may include measuring,acquiring, and/or determining real-time information relating to writelatencies for IO activities associated with the Service(s) which havebeen assigned to handle write and/or replication operations for theidentified Client.

As shown at 1706, the QoS Client-Write Policy Management Procedure maydetermine a current Load(Client-Write) value for the identified Client.According to different embodiments, the Load(Client-Write) value may bedetermined or calculated, for example, using one or more of the variousLoad(Client-Write) calculation techniques described herein. In at leastone embodiment, the Load(Client-Write) value may be expressed as aclient-specific Load value which takes into account write latencymetrics for IO activities associated with the Service(s) which have beenassigned to handle write and replication operations for the identifiedClient.

As shown at 1708, the QoS Client-Write Policy Management Procedure mayanalyze the current Load(Client-Write) value, and in response, mayselect and implement an appropriate QoS Management Policy for theidentified Client. For example, as illustrated in the example embodimentof FIG. 17:

-   -   If it is determined that Load(Client-Write)<Threshold Value A1,        the QoS Client-Write Policy Management Procedure may implement        (1710) QoS Management Policy Set A3;    -   If it is determined that Threshold Value        A1≧Load(Client-Write)≧Threshold Value A2, the QoS Client-Write        Policy Management Procedure may implement (1712) QoS Management        Policy Set B3;    -   If it is determined that Load(Client-Write)>Threshold Value A2,        the QoS Client-Write Policy Management Procedure may implement        (1716) QoS Management Policy Set C1.

FIG. 21 shows a graphical representation illustrating an exampleembodiment of how different QoS Management Policy Sets for throttlingClient IOPS may be automatically and/or dynamically implemented inresponse changing Load(Client-Write) conditions. As illustrated in theexample embodiment of FIG. 21, an X-Y graph portion 2100 is shown whichincludes a Y-axis representing target performance values correspondingto client write IOPS 2110 and an X-axis representing Load(Client-Write)values for a selected Client (e.g., Client A). As illustrated in theexample embodiment of FIG. 21, graph portion 2100 includes referencelines 2103, 2105, 2107 which represent the min write IOPS QoS parameter2103; max write IOPS QoS parameter 2105; and max burst write IOPS QoSparameter 2107 for the identified Client. Additionally, graph portion2100 includes reference lines 2111, 2113, 2115 which, in this exampleembodiment, represent threshold values which may be used to determineand select the current QoS Management Policy Set to be put into effectfor the identified Client. For example, as illustrated in FIG. 21:

-   -   During times when Load(Client-Write)<Threshold Value A1, QoS        Management Policy Set A3 may be set into effect for the        identified Client. In the specific example embodiment of FIG.        21, region 2102 provides a graphical representation of the        possible values of IOPS that a client can operate at in        accordance with the QoS Management Policy Set A3. In this        example embodiment, the QoS Management Policy Set A3 may specify        that the Client is allowed to accrue IOPS credits, and that the        Client's IOPS: can be equal to or less than the Client's max        IOPS QoS parameter 2105; may be allowed to operate above the        Client's max burst IOPS QoS parameter based upon accrued        credits; but is not to exceed the Client's max burst IOPS QoS        parameter 2107.    -   During times when Threshold Value        A3≧Load(Client-Write)≧Threshold Value A2, QoS Management Policy        Set B3 may be set into effect for the identified Client. In the        specific example embodiment of FIG. 21, region 2104 provides a        graphical representation of the possible values of IOPS that a        client can operate at in accordance with the QoS Management        Policy Set B1. In this example embodiment, the QoS Management        Policy Set B3 may specify that the Client's write IOPS are to be        throttled to a target performance IOPS value which is within a        range between the Client's max write IOPS QoS parameter and min        write IOPS QoS parameter. Additionally, the QoS Management        Policy Set B1 may also specify that, at any given time (while        Threshold Value A1≧Load(Client-Write)≧Threshold Value A2), the        Client's write IOPS are to be throttled to a target performance        IOPS value which is dynamically determined based on the Client's        current (e.g., real-time) Load(Client-Write) value. For example,        in the example embodiment of FIG. 21, while the QoS Management        Policy Set B3 is in effect, the Client's write IOPS are to be        throttled to a target performance IOPS value which does not        exceed the corresponding IOPS value defined by boundary curve        2104 a (e.g., which defines the upper limit of the Client's        allowable write IOPS relative to the Client's current        Load(Client-Write) value).    -   During times when Load(Client-Write)>Threshold Value A2, QoS        Management Policy Set C3 may be set into effect for the        identified Client. In the specific example embodiment of FIG.        21, region 2106 provides a graphical representation of the        possible values of IOPS that a client can operate at in        accordance with the QoS Management Policy Set C3. In this        example embodiment, the QoS Management Policy Set C3 may specify        that the Client's write IOPS are to be throttled to a target        performance IOPS value which is within a range between the        Client's min write IOPS QoS parameter and zero. Additionally,        the QoS Management Policy Set C3 may also specify that, at any        given time (Load(Client-Write)>Threshold Value A2), the Client's        write IOPS are to be throttled to a target performance IOPS        value which is dynamically determined based on the Client's        Load(Client-Write) value. For example, in the example embodiment        of FIG. 21, while the QoS Management Policy Set C3 is in effect,        the Client's write IOPS are to be throttled to a target        performance IOPS value which does not exceed the corresponding        IOPS value defined by boundary curve 2106 a (e.g., which defines        the upper limit of the Client's allowable write IOPS relative to        the Client's current Load(Client-Write) value).

In at least one embodiment, at least a portion of the various QOStechniques described herein may be based, at least in part, on theability for the storage system to dynamically implement individuallycustomized QoS Management Policies across multiple different Clients ofa given cluster.

In an alternate embodiment, when the storage system determines that acluster is overloaded, the system may use a sliding scale toproportionally and evenly throttle the IOPS associated with each Clientof the cluster. As the system overload increases, each Client's IOPS maybe automatically, dynamically and/or proportionally backed down (orthrottled) based on each Client's respective, updated target IOPS value.Since, the max IOPS and min IOPS QoS parameters may differ for eachClient, the target performance IOPS value for each Client may differeven under similar system load conditions.

For example, at a 5 ms latency, the storage system may designate theLOAD of the system to be above a first threshold value (e.g.,LOAD(System)=70%), which, for example, may result in the systemimplementing a first QoS Management Policy Set which causes eachClient's IOPS to be throttled to a value somewhere near their respectivemin IOPS QoS parameter. When this occurs, there may be only limited waysto achieve higher performance on the cluster, such as, for example, byadding more capacity and/or by lowering the max IOPS QoS parameters ofvolumes. Alternatively, at smaller cluster latencies (e.g.,<˜2 ms), thestorage system may designate the LOAD of the system to be less than asecond threshold value (e.g., LOAD(System)=30%), and the system mayimplement a second QoS Management Policy Set which allows clients tocontinue to burst and go above their max IOPS QoS parameter. Inembodiments where the cluster is not considered to be overloaded (e.g.,the read latencies are acceptable, and write cache queue(s) aresufficiently low), the cluster load may not affect the final targetperformance IOPS value. Thus, for example, if Client A's max IOPS QoSparameter is set to 1000 IOPS, and Client A's max burst IOPS QoSparameter is set to 1500 IOPS, then, under non-loaded conditions, thesystem may set Client A's target performance IOPS value to be within therange of 1000 to 1500 IOPS.

Clients Operating Above Their Max QoS Parameter (Bursting)

FIG. 7 depicts a graph 700 of a number of IOPS performed by client 108over a time period according to one implementation. A Y-axis shows thenumber of IOPS performed per second. Periods of a half second are shownon the X-axis. Credits are shown that are accumulated when the number ofIOPS is below the max IOPS level (100 IOPS). As shown, credits increasegradually from time periods 1-8. At time period 8, the client hasaccrued roughly 320 credits, as indicated by bar 702. As client 108bursts above the max IOPS value, the number of credits starts todecrease. In graph 700, the client is using roughly 125 IOPS, as shownby square 704, in time period 9. The client is allowed to burst abovetheir max IOPS level, since they have accrued credits, as shown by thebar 702. The client's IOPS level is capped at their burst IOPS value. Inthe graph 700, the client reaches their burst IOPS value in time periods10 and 11. When the client is operating above their max IOPS value,their credits are decreased. In one implementation, the amount ofcredits decreased is equal to amount of IOPS over the client's max IOPSvalue. From time period 13 on, client 108 is operating at the max IOPSlevel and the number of credits does not increase.

Credits can be accrued based upon client metrics. For example, in oneembodiment, for each IO operation that the Client does not utilize whilethe Client's IOPS are below a specified threshold (e.g., while theClient's IOPS are below the Client's max IOPS value), the Client mayreceive an “IOP credit” that may be subsequently used (when allowed bythe system) to enable the Client's IOPS to burst above the Client's maxIOPS value. For instance, if it is assumed that the Client's max IOPSvalue is set at 1000 IOPS, and the Client's max burst IOPS value is setat 1500 IOPS, and it is further assumed that the Client is currentlyonly using 900 IOPS and that the system is not overloaded, the Clientmay accrue 100 IOPS credits (e.g., each second) which may besubsequently used enable the Client's IOPS to burst above 1000 IOPS.

According to different embodiments, one or more limitations orrestrictions may be imposed with regards to IOPS burst activities suchas, for example, one or more of the following (or combinations thereof):

The total IOPS Credits (e.g., for a given Client and/or for a givencluster) may be capped at a certain amount. For example, in oneembodiment, for a given Client, the total IOPS Credits which may beaccrued by that Client may be determined according to:

Total IOPS Credits=(max burst IOPS value−max IOPS value)*burst time.

Thus, in one example embodiment where burst time is set at 10 seconds,the Client may accrue a maximum of (1500−1000)*10=5000 IOPS credits.

The Client may be limited to using only an allotted portion of itsaccrued IOPS credits during a given time interval. For example, eventhough the Client may accrue 5000 credits, the Client may be permittedto use no more than 500 (e.g., 1500−1000=500) of its 5000 credits duringone or more specific time intervals. In addition, bursting can belimited based upon the QoS policy sets as described above.

Slice Server Rebalancing

As described above, a volume server 122 can be associated with one ormore slice servers 124. Each slice server 124 stores metadata associatedwith a volume within the system 100. In one implementation, a new slicefor a newly created volume can be placed on a volume server 122 basedupon the capacity of the volume server 124. For example, a volume server122 with more free storage capacity can be selected over other volumeservers with less free storage capacity. The placement of the new slice,however, may not be ideal with reference to the load of the volumeserver 122, which can impact the quality of service for a clientaccessing the new volume. To gain a better distribution of slices, loadvalues, system metrics, client metrics, and QoS parameters describedabove can be used to determine when and where to place a client'sslices. For example, min QoS parameters can be summed on a particularservice. This summed value can be used to ensure that the service cansupport the requested QoS of the clients. Slices can be placed and/ormoved based upon this summed value across various services.

In one implementation, the QoS parameters of clients are used todetermine a target quality of service index of a particular volumeserver. For example, all clients that have a slice server on aparticular volume server can be determined. The minimum IOPS or maximumIOPS for each client can be summed. If this value is above apredetermined threshold, a decision to move one or more slices is made.When the sum is above the threshold, an alert can be sent toadministrators of the system. The administrator can then determine whichslice to move to another slice server. In an alternative embodiment, themove can occur automatically in such a way that evens the quality ofservice index for each of the slice servers, by selecting an unloadedvolume server. In addition to identifying which volume server isoverloaded, underutilized volume servers can also be identified in asimilar manner. A sum of the minimum IOPS for each volume server can becalculated and displayed to the administrators. The administrators canthen intelligently select a new volume server. In anotherimplementation, a slice can be moved automatically based upon detectingan overloaded volume server.

In addition to using the QoS parameters, performance metrics and loadvalues described above can be used to determine if a volume isoverloaded and which volumes are not overloaded. For example, thewrite-cache capacity of a volume server can be used in conjunction witha client's metrics to determine when and which slice to move. A processcan monitor the various system level metrics, such as a volume server'swrite cache capacity, and determine if any volume server is overloaded.Similar to the target performance manager 402 described above, anoverloaded condition can be determined based upon comparing load valueswith corresponding thresholds. If an overload condition is detected, theclient metrics, system metrics, and/or load values can be used todetermine if any clients are unproportionally responsible for theoverload condition. For example, a volume server can have slices and/orslice servers for a number of clients. Two such clients may account fora large amount of data writes on the volume server which impacts thevolume server's write cache capacity. Using the number of IO writes, theamount of written bandwidth of all of the clients, and/or load valuesassociated with number of IO writes and/or bandwidth, the two clientswho are impacting the write cache capacity more than other clients canbe determined. Based upon this characteristic, a slice associated witheither of these two clients can be selected to be moved to anothervolume server. This feature helps ensure that moving a particular sliceoff of a volume will have a significant impact in reducing oreliminating the overload condition for the other clients on the system.Without investigating the client metrics, system metrics, and/or loadvalues, a slice could be moved that is not significantly impacting theperformance of a volume server. This scenario can result in the originalvolume server still being overloaded.

In addition, the performance metrics and/or load values associated withthe other volume servers can be analyzed to find a volume server for aslice. Continuing the above example, a volume server that can handle alarge amount of writes can be determined. For example, volume serverswith a large write cache capacity or that have a relatively small numberof write IOs across all customers of the volume server can be identifiedthrough either performance metrics or load values. The slice can then bemoved to one of these identified volume servers, helping to ensure thatmoving the slice will not cause an overload condition for the new volumeserver based upon moving the slice server.

In one implementation, slice server rebalancing can be doneindependently from quality of service monitoring. For example, checkingto determine if any slice should be moved can be done on a schedule,e.g., every 500 ms, 1 s, 1 minute, etc. In another implementation, thequality of service monitoring and slice server rebalancing can beintegrated. For example, prior to checking the quality of service forclients, the slice server rebalancing process can be queried todetermine if any slice should be moved. If any volume server isoverloaded, the quality of service monitoring can wait until the sliceis moved. As an overloaded volume server can impact performance metricsand load values of the system and clients, the quality of servicemonitoring may wait until after the slice servers are rebalanced. Thisfeature allows the quality of service monitoring to use performancemetrics and/or load values that adequately describe system performanceand client performances without being negatively impacted by anoverloaded volume server.

One or more flow diagrams have been used herein. The use of flowdiagrams is not meant to be limiting with respect to the order ofoperations performed. The herein-described subject matter sometimesillustrates different components contained within, or connected with,different other components. It is to be understood that such depictedarchitectures are merely exemplary, and that in fact many otherarchitectures can be implemented which achieve the same functionality.In a conceptual sense, any arrangement of components to achieve the samefunctionality is effectively “associated” such that the desiredfunctionality is achieved. Hence, any two components herein combined toachieve a particular functionality can be seen as “associated with” eachother such that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality,and any two components capable of being so associated can also be viewedas being “operably couplable” to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents and/or wirelessly interactable and/or wirelessly interactingcomponents and/or logically interacting and/or logically interactablecomponents.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.”

The foregoing description of illustrative implementations has beenpresented for purposes of illustration and of description. It is notintended to be exhaustive or limiting with respect to the precise formdisclosed, and modifications and variations are possible in light of theabove teachings or may be acquired from practice of the disclosedimplementations. It is intended that the scope of the invention bedefined by the claims appended hereto and their equivalents.

What is claimed is:
 1. A method comprising: receiving client quality ofservice values associated with a first client; determining clientmetrics of a volume in a storage system based upon use of the volume bythe first client, wherein the storage system stores data from aplurality of clients, and wherein the client metrics reflect usage ofthe storage system by the first client; determining, using a processor,a client load value based upon the client metrics; determining a qualityof service management policy for the first client from a plurality ofquality of service management policies based upon the client load value,wherein each quality of service management policy comprises a formula,and wherein at least one formula includes a variable; calculating aclient target performance value based upon the formula of the quality ofservice management policy that includes the variable, a value of thevariable, and the received client quality of service values; adjustingperformance of the storage system for the first client based upon theclient target performance value; and adjusting performance of thestorage system for a second client of the storage system based upon asecond formula and different client target performance value associatedwith the second client.
 2. The method of claim 1, wherein the variableis the client load value.
 3. The method of claim 2, wherein the clientload value represents a client write load value.
 4. The method of claim1, further comprising setting a maximum quality of service parameter forthe first client to a maximum quality of service value, wherein theclient quality of service values include the maximum quality of servicevalue, and wherein the formula of at least one quality of servicemanagement policy is based upon the maximum quality of serviceparameter.
 5. The method of claim 4, wherein the calculated clienttarget performance value is based on the maximum quality of servicevalue.
 6. The method of claim 4, further comprising setting a maximumburst quality of service parameter for the first client to a maximumburst quality of service value, wherein the client quality of servicevalues include the maximum burst quality of service value, wherein theformula of at least one quality of service management policy is basedupon the maximum burst quality of service parameter, and wherein thecalculated client target performance value for the client is above themaximum quality of service value and below or equal to the maximum burstquality of service value.
 7. The method of claim 4, further comprising:receiving a request to increase the maximum quality of service value fora time period; setting the maximum quality of service parameter for thefirst client to an increased maximum quality of service value for thetime period; and resetting the maximum quality of service parameter tothe maximum quality of service value after expiration of the timeperiod.
 8. The method of claim 1, further comprising setting a minimumquality of service parameter for the first client to a minimum qualityof service value, wherein the client quality of service values includethe minimum quality of service value, wherein the formula of at leastone quality of service management policy is based upon the minimumquality of service parameter, and wherein the calculated client targetperformance value for the client is below the minimum quality of servicevalue.
 9. The method of claim 1, further comprising: receiving aschedule of quality of service values associated with the first clientthat includes quality of service values, wherein each quality of servicevalues is associated with a date or a time of day; and determining theclient quality of service values to use in calculating the client targetperformance value based upon the schedule of quality of service values.10. The method of claim 1, wherein the determining the client load valuebased upon the client metrics comprises adding a plurality of clientmetrics, wherein each client metric is multiplied by a weightedvariable.
 11. A non-transitory computer-readable medium havinginstructions stored thereon, that when executed by a computing devicecause the computing device to perform operations comprising: receivingclient quality of service values associated with a first client;determining client metrics of a volume in a storage system based uponuse of the volume by the first client, wherein the storage system storesdata from a plurality of clients, and wherein the client metrics reflectusage of the storage system by the first client; determining a clientload value based upon the client metrics; determining a quality ofservice management policy for the first client from a plurality ofquality of service management policies based upon the client load value,wherein each quality of service management policy comprises a formula,and wherein at least one formula includes a variable; calculating aclient target performance value based upon the formula of the quality ofservice management policy that includes the variable, a value of thevariable, and the received client quality of service values; adjustingperformance of the storage system for the first client based upon theclient target performance value; and adjusting performance of thestorage system for a second client of the storage system based upon asecond formula and different client target performance value associatedwith the second client.
 12. The non-transitory computer-readable mediumof claim 11, wherein the operations further comprise setting a maximumquality of service parameter for the first client to a maximum qualityof service value, wherein the client quality of service values includethe maximum quality of service value, and wherein the formula of atleast one quality of service management policy is based upon the maximumquality of service parameter.
 13. The non-transitory computer-readablemedium of claim 12, wherein the calculated client target performancevalue is based on the maximum quality of service value.
 14. Thenon-transitory computer-readable medium of claim 12, wherein theoperations further comprise setting a maximum burst quality of serviceparameter for the first client to a maximum burst quality of servicevalue, wherein the client quality of service values include the maximumburst quality of service value, wherein the formula of at least onequality of service management policy is based upon the maximum burstquality of service parameter, and wherein the calculated client targetperformance value for the client is above the maximum quality of servicevalue and below or equal to the maximum burst quality of service value.15. The non-transitory computer-readable medium of claim 12, wherein theoperations further comprise: receiving a request to increase the maximumquality of service value for a time period; setting the maximum qualityof service parameter for the first client to an increased maximumquality of service value for the time period; and resetting the maximumquality of service parameter to the maximum quality of service valueafter expiration of the time period.
 16. The non-transitorycomputer-readable medium of claim 11, wherein the operations furthercomprise setting a minimum quality of service parameter for the firstclient to a minimum quality of service value, wherein the client qualityof service values include the minimum quality of service value, whereinthe formula of at least one quality of service management policy isbased upon the minimum quality of service parameter, and wherein thecalculated client target performance value for the client is below theminimum quality of service value.
 17. A system comprising: one or moreprocessors configured to: receive client quality of service valuesassociated with a first client; determine client metrics of a volume ina storage system based upon use of the volume by the first client,wherein the storage system stores data from a plurality of clients, andwherein the client metrics reflect usage of the storage system by thefirst client; determine a client load value based upon the clientmetrics; determine a quality of service management policy for the firstclient from a plurality of quality of service management policies basedupon the client load value, wherein each quality of service managementpolicy comprises a formula, and wherein at least one formula includes avariable; calculate a client target performance value based upon theformula of the quality of service management policy that includes thevariable, a value of the variable, and the received client quality ofservice values; adjust performance of the storage system for the firstclient based upon the client target performance value; and adjustperformance of the storage system for a second client of the storagesystem based upon a second formula and different client targetperformance value associated with the second client.
 18. The system ofclaim 17, wherein the one or more processors are further configured toset a maximum quality of service parameter for the first client to amaximum quality of service value, wherein the client quality of servicevalues include the maximum quality of service value, and wherein theformula of at least one quality of service management policy is basedupon the maximum quality of service parameter.
 19. The system of claim18, wherein the calculated client target performance value is based onthe maximum quality of service value.
 20. The system of claim 18,wherein the one or more processors are further configured to set amaximum burst quality of service parameter for the first client to amaximum burst quality of service value, wherein the client quality ofservice values include the maximum burst quality of service value,wherein the formula of at least one quality of service management policyis based upon the maximum burst quality of service parameter, andwherein the calculated client target performance value for the client isabove the maximum quality of service value and below or equal to themaximum burst quality of service value.